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Embry, Bruce A. "Finding alternatives to the hard disk drive for virtual memory /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2985.pdf.
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Embry, Bruce Albert. "Finding Alternatives to the Hard Disk Drive for Virtual Memory." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1727.
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Current computer systems fill the demand of operating systems and applications for ever greater amounts of random access memory by paging the least recently used data to the hard disk drive. This paging process is called "virtual memory," to indicate that the hard disk drive is used to create the illusion that the computer has more random access memory than it actually has. Unfortunately, the fastest hard disk drives are over five orders of magnitude slower than the DRAM they are emulating. When the demand for memory increases to the point that processes are being continually saved to disk and then retrieved again, a process called "thrashing" occurs, and the performance of the entire computer system plummets. This thesis sought to find alternatives for home and small business computer users to the hard disk drive for virtual memory which would not suffer from the same long delays. Virtual memory is especially important for older computers, which often are limited by their motherboards, their processors and their power supplies to a relatively small amount of random access memory. Thus, this thesis was focused on improving the performance of older computers by replacing the hard disk drive with faster technologies for the virtual memory. Of the different technologies considered, flash memory was selected because of its low power requirements, its ready availability, its relatively low cost and its significantly faster random access times. Two devices were evaluated on a system with a 512MB of RAM, a Pentium 4 processor and a SATA hard disk drive. Theoretical models and a simulator were developed, and physical performance measurements were taken. Flash memory was not shown to be significantly faster than the hard disk drive in virtual memory applications.
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Wu, Xiaohua Sherry. "Innovation incentives and competition in the hard disk drive industry." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69479.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Economics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 52-53).
Firms in the hard disk drive industry are continually engaging in R & D and improving the quality of their products. We explore various determinants of the product innovation incentives for firms concerned with both their static and expected future profitability. We estimate the observed innovation outcomes as a function of market condition variables which have significant impact on innovation decisions. In addition, we estimate logit utilities that describe the marginal willingness to pay for quality improvements. One aspect of utility is that the willingness to pay for faster access time to data may be initially low but increases over time. The firms' decisions to introduce faster access time are partly motivated by dynamic considerations.
by Xiaohua Sherry Wu.
S.M.
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Ray, William H. (William Hamilton). "The reduction of acoustic noise emissions from a hard disk drive." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34324.
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Yasuda, Takeo. "Circuit Technologies for High Performance Hard Disk Drive Data Channel LSI." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150621.
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Wallberg, John Leonard. "A digital phase-locked loop for hard disk drive read channel appliations." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42726.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 78).
by John Leonard Wallberg.
M.Eng.
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Collins, Jill. "Modelling tribology of slider and disk in a computer hard drive system." Thesis, Aston University, 2001. http://publications.aston.ac.uk/7995/.
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Issues of wear and tribology are increasingly important in computer hard drives as slider flying heights are becoming lower and disk protective coatings thinner to minimise spacing loss and allow higher areal density. Friction, stiction and wear between the slider and disk in a hard drive were studied using Accelerated Friction Test (AFT) apparatus. Contact Start Stop (CSS) and constant speed drag tests were performed using commercial rigid disks and two different air bearing slider types. Friction and stiction were captured during testing by a set of strain gauges. System parameters were varied to investigate their effect on tribology at the head/disk interface. Chosen parameters were disk spinning velocity, slider fly height, temperature, humidity and intercycle pause. The effect of different disk texturing methods was also studied. Models were proposed to explain the influence of these parameters on tribology. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were used to study head and disk topography at various test stages and to provide physical parameters to verify the models. X-ray Photoelectron Spectroscopy (XPS) was employed to identify surface composition and determine if any chemical changes had occurred as a result of testing. The parameters most likely to influence the interface were identified for both CSS and drag testing. Neural Network modelling was used to substantiate results. Topographical AFM scans of disk and slider were exported numerically to file and explored extensively. Techniques were developed which improved line and area analysis. A method for detecting surface contacts was also deduced, results supported and explained observed AFT behaviour. Finally surfaces were computer generated to simulate real disk scans, this allowed contact analysis of many types of surface to be performed. Conclusions were drawn about what disk characteristics most affected contacts and hence friction, stiction and wear.
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Sládek, Petr. "Disková pole RAID a jejich budoucnost v éře SSD." Master's thesis, Vysoká škola ekonomická v Praze, 2012. http://www.nusl.cz/ntk/nusl-124667.
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The thesis aims at verification of using emerging Solid-State drives in disk arrays. The advent of SSD disks caused a small revolution in area of data storage, because the growth performance of hard drives has been slow compared to other PC components. But an entirely different principle of operation could mean compatibility problems between SSD and related technologies, such as RAID. This thesis aims at analyzing all the relevant technologies, mainly HDD, SSD and RAID. To achieve this objective, information from literature, articles and other appropriate sources will be used. Other objectives of this thesis are to determine how much are the SSDs suitable for use in the disk array, because low performance RAID controllers or different principles of operation could limit their efficiency. This question should be answered by submission of selected types of storage arrays to synthetic and practical tests of performance. The final goal is to use financial analysis of the test solutions as a shared file storage. Today, remote access to data is used by a wide range of job positions. Slow storage could mean inefficient use of working time and therefore unnecessary financial costs. The goal of my work is primarily to provide answers to the questions mentioned above. Currently it is very hard to find tests of more complex forms of disk arrays based on solid-state drives. This article can be also very useful for companies where fileservers are used to share user data. Based on the result of cost analysis, the company can then decide what type of storage is best for its purpose.
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Chiu, Wan Ting. "The innovator's dilemma? : re-thinking disruptive technology in the hard disk drive industry /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?SOSC%202006%20CHIU.
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Méndez, de la Luz Diego A. 1979. "The role of heat assisted magnetic recording in future hard disk drive applications." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28872.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references.
(cont.) portable consumer electronics, such as PDAs, cell phones, music players, digital cameras, etc. make a relatively modest but fast growing market for ultrahigh areal density HAMR-based HDDs. HAMR-based HDD for portable applications could very well be a disruptive technology in the magnetic recording industry. Companies that intend to profit from this technology need to invest on its development and must try to be first-to-volume production to benefit from economies of scale and to build the necessary expertise that could give them leadership roles in future magnetic recording.
The magnetic recording industry keeps up with the demand of high capacity hard disk drives by improving the areal recording density of these devices. The use of conventional longitudinally magnetized media will be truncated by the challenges it faces nowadays, which are related to the instability of the stored information, produced by the aggressive decrease in the volume of the grains in the media. To overcome this problem, the use of large magnetic anisotropy energy density alloys is necessary, but the write fields that are required by such alloys can be prohibitively large, rendering these media effectively unwritable. Fortunately, the magnetocrystalline anisotropy energy density decreases with increasing temperature and so does the required write field. Heat assisted magnetic recording allows the use of such magnetically hard alloys by using both a magnetic and a thermal field during the writing process. Research in HAMR is centered in three major fields: the heat delivery system, the magnetic recording media and the heat dissipation technology. Based on an analysis of several US patents related to HAMR, one can see the real value of such patents is in negotiating and cross-licensing between companies to guarantee the right to participate in the manufacture of HDDs. Trade secrets and know-how are valuable assets for corporations. However, information exchange exists due to the great mobility of highly trained personnel between competing companies. Because the basic application of HAMR is in supplying the computer industry with affordable storage devices, there is a well established market that makes the research efforts in HAMR advisable for individuals, universities and companies. Besides that traditional market,
by Diego A. Méndez del la Luz.
M.Eng.
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Bhasin, Harpreet. "An Evolutionary Algorithm for Feature Subset Selection in Hard Disk Drive Failure Prediction." NSUWorks, 2011. http://nsuworks.nova.edu/gscis_etd/91.
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Hard disk drives are used in everyday life to store critical data. Although they are reliable, failure of a hard disk drive can be catastrophic, especially in applications like medicine, banking, air traffic control systems, missile guidance systems, computer numerical controlled machines, and more. The use of Self-Monitoring, Analysis and Reporting Technology (SMART) can aid in failure prediction by monitoring specific drive attributes and warning the user of an impending failure so that the user can backup data while there is still time. As a consequence, hard drive failure prediction has become an important problem and the subject of active research.
The best available approaches for hard drive failure prediction achieve acceptably low false alarm rates by first selecting a subset of features using non-parametric statistical methods such as reverse arrangements and then using the multiple-instance naïve Bayes classifier for the prediction task. However, the prediction accuracy of this approach is not sufficiently high.
The focus of this dissertation was to improve the drive failure prediction accuracy while maintaining a low false alarm rate by using a genetic algorithm for feature set reduction in conjunction with the multiple-instance naïve Bayes classifier for the prediction task. This research achieved a failure detection rate of 81% with a 0% false alarm rate on 12 attributes selected by the genetic algorithm. As a secondary contribution, this dissertation investigated the tradeoff between feature subset reduction and prediction accuracy in the hard drive prediction problem. This research found that as the number of features decreased below 10, the detection accuracy decreased significantly.
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Slade, Christopher Ryan. "On-Disk Sequence Cache (ODSC): Using Excess Disk Capacity to Increase Performance." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1020.pdf.
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Zhu, Xi. "High frequency CMOS integrated filters for computer hard disk drive and wireless communication systems." Thesis, University of Hertfordshire, 2008. http://hdl.handle.net/2299/2069.
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Operational transconductance amplifier and capacitor (OTA-C) filters have outstood among different types of filter due to high frequency and low power capabilities in the main stream digital CMOS technology. They have been widely used in computer hard disk drive (HDD) and wireless communication transceivers. OTA-C filters based on cascade and passive ladder simulation are well-known. However, multiple loop feedback (MLF) OTA-C filters which have certain advantages still have the scope for further research. So far there have been no explicit formulas for current-mode leapfrog (LF) filter design and performance evaluation of current-mode MLF OTA-C filters are still lacking. From application viewpoints, read channels for computer hard disk drives require very high frequency continuous-time filters. This automatically disqualifies active- RC/MOSFET-C filters and OTA-C filters become the only solution. In wireless communications, active-RC/MOSFET-C filters have been proved useful for mobile systems whose baseband frequency falls below a few MHz. However, for wireless LANs with the frequency of several tens of MHz, OTA-C filters are a strong candidate. Whilst in HDD read channels, cascaded OTA-C architectures have been most utilized and in wireless receivers, OTA-C structures based on ladder simulation have been popular, MLF OTA-C filters have not been practically used in either of the applications. This thesis describes some novel designs and applications of multiple loop feedback OTA-C filters with extensive CMOS simulations. Analogue filters for computer hard disk drive systems are first reviewed; the state of the art and design considerations are provided. Three VHF linear phase lowpass OTA-C filters are then designed, which include a seventh-order and a fifth-order current-mode filter based on the follow-the-leader-feedback (FLF) structure and a seventh-order voltage-mode filter using the inverse FLF (IFLF) configuration. These filters all have very low power consumption. The synthesis and design of general current-mode LF OTA-C filters are conducted next. Iterative design formulas for both all-pole and finite-zero functions are derived and explicit formulas for up to sixth-orders are given. These formulas are very easy to use for designing any type of characteristics. Subsequently, linear phase lowpass OTA-C filter design for HDD read channels using LF structures are investigated in details. A current-mode filter and a voltage-mode filter using the fifth-order LF structure are presented. The two filters can operate up to 800MHz and have very small passband phase ripple. Analogue filters for wireless communication baseband applications are also reviewed thoroughly in this thesis, where the design of a fourth-order current-mode FLF Butterworth lowpass OTA-C filter for multi-standard receivers is presented. Then two fifth-order current-mode elliptic lowpass OTA-C filters based on respective LF and FLF structures for wireless communication baseband are designed. Fifth-order voltage-mode IFLF and LF elliptic lowpass filters are also presented. All these MLF baseband filters designed can operate up to 40MHz to cover all important wireless and mobile standards. Simulations show that the LF structures have better dynamic range and stopband attenuation performances than the FLF and IFLF configurations.
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Semati, Massimiliano. "Soluzioni per il controllo delle testine di lettura/scrittura in hard disk drive magnetici." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11748/.
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Questa tesi descrive alcune tecniche realizzative e algoritmi di controllo per il posizionamento delle testine di lettura/scrittura in hard disk drive magnetici. Viene presentata l'attuazione a due stadi delle testine per incrementare la banda frequenziale del sistema, in cui un motore VCM funge da primo stadio e come secondo stadio si utilizza un microattuatore, di tipo piezoelettrico o elettromagnetico o elettrotermico. Il posizionamento della testina sulle tracce magnetiche dei dischi contenenti i dati si divide in due fasi: track-seeking e track-following, che presentano diversi requisiti di velocità e precisione, per questo motivo si descrive il metodo dello switching control. Successivamente viene formulato un modello matematico nello spazio degli stati degli stati dell'attuatori a due stadi e il relativo controllo in retroazione, basato su osservatore dello stato. Inoltre per il track-seeking si propone il controllo a due gradi di libertà e per il track-following il metodo del disaccoppiamento della sensitività. Infine si riportano due novità tecnologiche per gli hard disk magnetici: l'attuazione a tre stadi, che sfrutta un secondo microattuatore, di tipo termico, e gli hard disk riempiti d'elio ed ermeticamente sigillati, che semplificano il controllo grazie alla minore turbolenza del gas e al suo minor peso.
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Lin, Yu-wei. "Benchmarked Hard Disk Drive Performance Characterization and Optimization Based on Design of Experiments Techniques." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/350.
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This paper describes an experimental study offered by Designs of Experiments (DOE) within the defined factor domains to evaluate the factor effects of simultaneous characteristics on the benchmarked hard disk drive performance by proposing well-organized statistical models for optimizations. The numerical relations of the obtained models permit to predict the behaviors of benchmarked disk performances as functions of significant factors to optimize relevant criteria based on the needs.
The experimental data sets were validated to be in satisfying agreement with predicted values by analyzing the response surface plots, contour plots, model equations, and optimization plots. The adequacy of the model equations were verified effectively by a prior generation disk drive within the same model family. The retained solutions for potential industrializations were the concluded response surface models of benchmarked disk performance optimizations.
The comprehensive benchmarked performance modeling procedure for hard disk drives not only saves experimental costs on physical modeling but also leads to hard-to-find quality improvement solutions to manufacturing decisions.
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Balasubramanian, Sanchayeni. "Improving Hard Disk Drive Write IO Performance with Phase Change Memory as a Buffer Cache." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511881125562903.
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Weissner, Stefan. "Numerical and experimental investigation of the load/unload behavior of subambient pressure hard disk drive sliders /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2001. http://wwwlib.umi.com/cr/ucsd/fullcit?p3027050.
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Chen, Feng. "On Performance Optimization and System Design of Flash Memory based Solid State Drives in the Storage Hierarchy." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1280537880.
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Virmani, Manish. "Shock-response analysis of a hard-disk drive in tilt-drop tests under non-operating and operating conditions." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p1430197.
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Weber, Michael A. "An Investigation of the Feasibility of Microscale Adaptive Passive Vibration Neutralizers." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32296.
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This thesis concerns the control of an adaptive passive vibration neutralizer and the feasibility of miniaturizing this type of tunable vibration neutralizer for small-scale applications.
An analytical model for the adaptive passive vibration neutralizer is derived and compared to experimental results. A tuning algorithm is derived from a curve-fit of experimental tests on the specific neutralizer. A more generic tuning algorithm is also developed, which does not require testing of the neutralizer for optimal control. Both tuning algorithms are tested using a chirp forcing function to simulate drift in the excitation frequency of a host structure. Computer simulation and experimental results are given for these tests.
A novel low-cost, small-scale vibration neutralizer is constructed from packing bubble-wrap. Analytical models for the stiffness are calculated, and experimental data is used to derive a damped mass-spring model.
Miniaturization of vibration neutralizers is described, and many of the pitfalls in design are discussed. Theoretical tuning frequencies of possible adaptive passive vibration neutralizers at different scales are included. The goal for these miniaturized vibration neutralizers is vibration control in computer hard drives.
A hard drive is analyzed for vibration problems. Included are plots of the velocities of the read-write head and spindle. Limitations of the measurement equipment are discussed, and directions for future work on small-scale tunable vibration neutralizers are outlined.
Master of Science
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Fang, Yeyu. "Titled and graded anisotropy FePt and FePtCu thin films for the application of hard disk drive and spin torque oscillators." Licentiate thesis, KTH, Mikroelektronik och tillämpad fysik, MAP, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34013.
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The FePt and FePtCu thin films with graded anisotropy and titled anisotropy are utilized to solve both the magnetic recording ‘‘trilemma’’ of the hard disk drives (HDDs) and the large field operation problem of spin torque oscillators (STOs). We have successfully realized the FePtCu thin films with graded anisotropy. During deposition a compositional gradient is achieved by continuously varying the Cu content from the top to bottom. After annealing at proper temperatures, the top Cu-poor regions remain at soft A1 phase, while the bottom Cu-rich regions transform into hard L1 0phase. Hence the gradient anisotropy is established through the film thickness. The critical role of the annealing temperatures (TA) on the resultant anisotropy gradient is investigated. Magnetic measurements support the creation of an anisotropy gradient in properly annealed films which exhibit both the reduced coercivity and moderate thermal stability. In conjunction of the fabrication, the subsequent analysis of the graded material is not trivial. The reversal mechanism of graded anisotropy have been investigated by alternation gradient magnetometer (AGM) and magneto optical Kerr effect (MOKE) measurements with first order reversal curves (FORC) technique. The AGM-FORC analysis, which clearly shows the soft and hard phases, is not able to resolve how these phases are distributed through the film thickness. MOKE-FORC measurement which preferentially probes the surface of the film, reveal that the soft components are indeed located toward the top surface. The TA plays a critical role in the induced anisotropy gradient. We provide a detailed study of the how the anisotropy gradient in a compositional graded FePtCu film gradually develops as a function of the TA. By utilizing the in-situ annealing and magnetic characterization capability of a physical property measurement system, the evolution of the induced anisotropy gradient is elucidated. These results are important and useful for the application of HDDs. In order to achieve the zero-field operation for STOs, we have successfully fabricated pseudo spinvalves based on L1 0(111) textured FePt or FePtCu. We demonstrate magnetoresistance(MR) in excess of 4% in FePt/CoFe/Cu/CoFe/NiFe pseudo spin valves based on L10(111)-oriented FePt fixed layers with a 36 ° out-of-plane tilted magnetization. The high MR is achieved by increasing the spin polarization at the Cu interfaces, using thin CoFe, and optimizing the FePt growth and Cu interface quality using Ta and Ta/Pt underlayers.We observe well-separated switching of the FePt/CoFe fixed layer and the CoFe/NiFe free layer, suggesting that CoFe is rigidly exchange coupled to FePt and NiFe in the respective layers. Futuremore, through optimization of the Cu spacer thickness, we demonstrate MR up to 5% in FePtCu/CoFe/Cu/CoFe/NiFe pseudo spin valves based on L10 (111) FePtCu fixed layers with a tilted magnetization. We find an optimum spacer thickness of about 2.4 nm which correlates with a clear onset of strong interlayer exchange coupling below 2.4 nm and spin-independent current shunting in the spacer above 2.4 nm. These results are an important milestone for future applications of tilted spin polarizers in STOs.QC 20110525
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Geier, Florian. "The differences between SSD and HDD technology regarding forensic investigations." Thesis, Linnéuniversitetet, Institutionen för datavetenskap (DV), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-44921.
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In the past years solid state disks have developed drastically and are now gaining increased popularity compared to conventional hard drives. While hard disk drives work predictable, transparent SSD routines work in the background without the user’s knowledge. This work describes the changes to the everyday life for forensic specialists; a forensic investigation includes data recovery and the gathering of a digital image of each acquired memory that provides proof of integrity through a checksum. Due to the internal routines, which cannot be stopped, checksums are falsified. Therefore the images cannot prove integrity of evidence anymore. The report proves the inconsistence of checksums of SSD and shows the differences in data recovery through high recovery rates on hard disk drives while SSD drives scored no recovery or very poor rates.
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Haq, Mohammad Ashraful. "Continuum and molecular dynamics analyses of lubricant evaporation and flow due to laser heating in heat-assisted magnetic recording." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531140850318054.
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Valkass, Robert Alexander James. "Exploration of the sub-nanosecond magnetisation dynamics of partially built hard disk drive write-head transducers and other topical magnetic and spintronic materials and devices." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/31175.
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In this thesis both the static and dynamic magnetic behaviour of complex three-dimensional nanoscale commercial hard disk drive write heads and thin film structures of interest to emerging spintronic devices have been investigated using a plurality of experimental techniques. The magneto-optical Kerr effect (MOKE) provides the basis for an optical microscopy technique sensitive to the magnetisation of a sample, detectable as a change in polarisation of light reflected from the sample surface. With a modelocked laser light source, synchronised electrical pulse generator and lock-in amplifier (LIA), a stroboscopic technique has been used to observe the magnetisation dynamics of hard disk drive write heads at 600 nm spatial resolution and 10 ps time resolution in response to a driving electrical pulse. The equilibrium magnetic state of these devices has been directly imaged by x-ray photo-emission electron microscopy (XPEEM), as well the stability of the equilibrium state in response to the application of an external bias field. Direct images of the equilibrium state obtained by XPEEM were found to agree with inferences made from MOKE images. Time-resolved scanning Kerr microscopy (TRSKM) images of magnetisation dynamics showed that flux does not form in ‘beams’ as commonly believed, but instead nucleates in separate sites across the writer. Static and time-resolved x-ray techniques have also been used to investigate a number of thin films of interest to spintronics. Spin pumping and spin transfer torque in Co2MnGe / Ag / Ni81Fe19 spin valves were explored using time-resolved x-ray ferromagnetic resonance (XFMR) carried out at Diamond Light Source (DLS), a as well as static x-ray magnetic circular dichroism (XMCD) for sample characterisation. This has provided element-specific measurements of the spin state in the source and sink layers of the spin valve, revealing a clear sign of spin transfer torque, while also investigating the role of sink layer thickness in spin pumping and damping. Ferrimagnetic yttrium iron garnet (Y3Fe2(FeO4)3) (YIG), a material of great interest in spintronics, has been studied by static and dynamic XMCD in comparison with ferromagnetic Co. While static and dynamic spectra for Co were identical, those for YIG differed markedly. While this may hint at a phase difference between the precession of Fe moments on different lattice sites, the true source of this difference has not been identified. Comparisons between vector network analyser ferromagnetic resonance (VNA-FMR) and XFMR measurements further suggest the presence of long-range inhomogeneities in the YIG. The spin dynamics of an antiferromagnet being driven by a ferromagnet have also been investigated using XMCD and x-ray magnetic linear dichroism (XMLD). A CoO / Fe / Ni81Fe19 trilayer wherein the thickness of the CoO layer varies across the sample has been thoroughly characterised by static XMCD and XMLD, providing information necessary to fully interpret time-resolved MOKE measurements on these samples. Measurements have shown that even small amounts of ordered CoO significantly modify the resonant field and linewidth of the adjacent ferromagnetic layers. Phase-resolved measurements of CoO spins have shown these spins to precess in phase with those of the adjacent Fe. The viability of dynamic XMLD measurements has also been confirmed. Finally, potential directions for future work in each project are discussed.
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Venkataramana, Vikash. "Neutrons to probe nanoscale magnetism in perpendicular magnetic recording media." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3187.
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Magnetic recording media refers to the disc shaped thin film magnetic medium present inside the hard disk drive of a computer. Magnetic recording is an important function of the hard disk drive by which information such as text, pictures, audio and videos are stored. Information is broken down to a simple binary format and is stored as magnetised bits along the tracks of the disk forming the hard drive. Over the years advancements in research on the type of magnetic materials used has allowed increased data storage capacities by reducing magnetic bit sizes. It is with this advancement in magnetic data storage, that we have today's hard disk drive technology, which uses a perpendicular magnetic medium to store data. A perpendicular magnetic medium is a multi-layered magnetic thin film structure with the topmost layer comprising nanoscale magnetic grains of high perpendicular anisotropy. The topmost recording layer (RL) is mapped into individual bits of 80-100 nm² area that consist of 5-10 nm diameter CoCrPt grains, embedded in an oxide matrix. A bit area is defined to ensure a significant number of stable grains allowing data to be stored in each bit as a ‘0' or a ‘1' depending on its switched magnetic state. The magnetic grains if sputtered below a threshold grain size tend to suffer from thermal fluctuation and instability due to super-paramagnetic effects, hence bringing limitations to grain size. As a result of this, research in recent years has been directed at introducing a softer magnetic exchange coupled composite (ECC) layer above the recording layer. This layer facilitates the delicate balance of switching smaller grains with strong magneto-crystalline anisotropy at lower magnetic fields, by exchange coupling with the CoCrPt grains in the recording layer. However this technique of increasing the efficiency in the perpendicular magnetic medium by introducing ‘facilitating' layers is an area that is still being widely researched and understood. Although numerous surface and bulk analysis techniques exist to study magnetic and surface properties of these materials, there is limited information on the structural and magnetic properties of these materials at the nanoscale level. The reported work investigates the structural and magnetic properties of the magnetic grains and multi-layers in the perpendicular magnetic medium using polarised neutron scattering and reflectivity techniques. The work investigates the structural and magnetic properties of the CoCrPt grains, apart from understanding the CoCrPt magnetic grain switching. The work also investigates the magnetisation in the layers of the thin film perpendicular media structure using polarised neutron reflectivity (PNR). Using polarised small angle neutron scattering (PolSANS), it has been shown that ferromagnetic ordered core region of the CoCrPt grain in the recording layer is smaller than the physical CoCrPt granular structure. The magnetic switching behaviour of the CoCrPt grain at different magnetic fields is also analysed and the experimental PolSANS data is fitted with non-interacting size-dependent analytical grain switching models. This result provides significant evidence that the magnetic anisotropy increases with grain size, with larger magnetic grains having larger magnetic anisotropy. Polarised neutron scattering experiments are carried out with the magnetically softer exchange coupled composite (ECC) layer included in the thin film magnetic structure. The first experiments investigate if the ECC layer contributes to the nuclear and magnetic interference scattering term in the experimenting scattering data. The experiments clearly show that there is no contribution from the ECC layer in the nuclear and magnetic scattering interference term. The role of the ECC layer in the magnetic switching process is then investigated at different magnetic fields. The ECC layer was found to influence the size-dependent magnetic grain switching of the CoCrPt grains in the recording layer and a detailed investigation is presented in the reported work. Polarised neutron reflectivity (PNR) experiments have also been carried out with the ECC layer on the perpendicular magnetic media samples. These experiments investigate the composition and thickness of the thin film structure, while also providing information on the magnetic state of the thin films under the influence of an in-plane magnetic field. The in-plane magnetisation in the recording and ECC layer is determined at different in-plane magnetic fields. The magnetisation values determined for the ECC layer and the recording layer (RL) at different in-plane magnetic fields help better understand the differences in their magnetic properties.
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Bengtsson, Johnny. "Forensisk hårddiskkloning och undersökning av hårddiskskrivskydd." Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2378.
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Detta examensarbete reder ut arbetsprinciperna för olika typer av hårddiskskrivskydd; hårdvaruskrivskydd, mjukvaruskrivskydd, hybridskrivskydd och bygelskrivskydd. Slutsatsen av utredningen är att endast hårdvaruskrivskydd Detta examensarbete reder ut arbetsprinciperna för olika typer av hårddiskskrivskydd; hårdvaruskrivskydd, mjukvaruskrivskydd, hybridskrivskydd och bygelskrivskydd. Slutsatsen av utredningen är att endast hårdvaruskrivskydd bedöms ha tillräckligt pålitliga skyddsprinciper, vilket motiveras av dess oberoende från både hårdvara och operativsystem.
Vidare undersöks hårdvaruskrivskyddet Image MASSter(TM) Drive Lock från Intelligent Computer Solutions (ICS). Några egentliga slutsatser gick inte dra av kretskonstruktionen, bortsett från att den är uppbyggd kring en FPGA (Xilinx Spartan-II, XC2S15) med tillhörande PROM (XC17S15APC).
En egenutvecklad idé till autenticieringsmetod för hårddiskkloner föreslås som ett tillägg till arbetet. Principen bygger på att komplettera hårddiskklonen med unik information om hårddisk såväl kloningsomständigheter, vilka sammanflätas genom XOR-operation av komponenternas hashsummor.Autenticieringsmetoden kan vid sjösättning möjligen öka rättsäkerheten för både utredarna och den som står misstänkt vid en brottsutredning.
Arbetet är till stora delar utfört vid och på uppdrag av Statens kriminaltekniska laboratorium (SKL) i Linköping.
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Li, Guijun, and 李桂君. "Development of recording technology with FePt recording media and magnetic tunnel junction sensors with conetic alloy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50899776.
Full textAbstract:
With highly demanding requirement in current emerging cloud storage and personal computers, hard disk drive recording with high stability and high volume has attached much attention in industry and academy. Recording media and recording head feasible for future high-density recording are both crucial to utilize magnetic recording with 1T bit/in2 recording density.
Recoding media with FePt for high density and high stability was investigated in this thesis using FePt polymers with imprinting methods and FePt thin films with ion-beam bombardment technologies. The FePt polymers can be patterned using imprint at micro-and nano-scales. The micro-and nano-patterns could be retained on substrates after sintering at high temperatures. The high magnetic coercivity was proved with line and dot patterns at different scales.
Recording heads with Al2O3based magnetic tunneling junction sensors were also studied in thesis. The magnetic tunneling junction sensors were proved to work stable at different temperatures varying from -30oC to 100oC. The long time running test up to 100 hours also proved the stability of the magnetic tunneling junction sensors working in extreme temperatures.
Withstate-of-art patterning and depositing technologies, new ideas about using FePt polymer to work as magnetic recording media and using ion beam bombardments to tune the FePt magnetic properties were verified. The feasibility of using Al2O3 based magnetic tunneling junction sensors as recording head was also discussed.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Mellachervu, Ramachandra Murthy. "Low voltage vertical recording preamplifier for hard disk drives." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1093.
Full textAbstract:
Higher data rate hard disk drives(HDD) and improved read channel electronics are demanding preamplifier performance be extended well beyond 1 Gb/s. Historically, preamplifier power requirements were of low priority; however, with increased demand for battery powered devices such as laptops, MP3 players, personal video recorders, andmanyother wireless hand-held devices, power consumption has become an important design parameter.Furthermore, in order to continue to increase drive capacities, new read-write head technologies(vertical recording and TGMR heads) are demanding innovative preamplifier circuitsolutions.Today's production preamplifiers possess a wide band response of 2.5 MHz-600 MHz; however next generation preamplifiers willrequire response greater than 250 KHz-1 GHz.Low corner frequencies below 250 KHz present read recovery (sleep-to-read, write-to-read, etc) challenges which can limit drive capacity. This project targets a > 2 Gb/s TGMR (tunneling giantmagneto-resistive) read path for verticalrecording HDDs. A high performance BiCMOS process (IBM's 0.5?m 5HP process)is essential due to the large transconductances, low noise and highspeed requirements of the read path's first stage. System frequency limitations at the input are a result of the large TGMR read sensor and preamplifier input capacitance. Due to read head and preamplifier manufacturingvariations, resistive feedbackaroundthe firststage is usedto seta controlled input impedance targeted to match the interconnect transmission line. Head resistance variations lead to gain variations; however, the TGMR element becomes more sensitive with larger resistance. This, to a first order approximation, acts like an automatic gain control and reduces variations in gain due to the head.
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Aravindakshan, Vibin. "Role of bit patterned media in future of hard disk drives." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42140.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references (p. 60-61).
The hard disk industry has traditionally stayed competitive by competing on the means of price alone by cutting down aggressively on cost via increase of areal density. Continuing increases in the areal density of hard disk drives will be limited by thermal instability of the thin film medium and is estimated to be limited to about 500Gb/in2. Patterned media, in which data are stored in an array of single.domain magnetic particles, have been suggested as a means to overcome this limitation and to enable recording densities greater than ITb/in2. However, the implementation of patterned media requires fabrication of sub-50-nm features over large areas and the design of recording systems that differ from those used in conventional hard drives. This report discusses the challenges facing patterned media, the fabrication of arrays of ́small magnetic particles and their magnetic properties. The practical implementation of patterned media recording schemes is assessed via technology estimates and cost analysis.
by Vibin Aravindakshan.
M.Eng.
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Hylick, Anthony Nelson. "Managing energy consumption of hard disk drives by optimizing system interaction." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608699.
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Brunner, Ralf. "Properties of carbon overcoats and perfluoro-polyether lubricants in hard disk drives." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3360154.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed August 11, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Sepasi, Daniel. "Modeling of linear systems with parameter variations : applications in hard disk and ball screw drives." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36869.
Full textAbstract:
This thesis considers variations in the parameters of the dynamics of linear systems, and tackles modeling of Linear Time-Invariant (LTI) and Linear Parameter Varying (LPV) plants. The variations in the dynamics make the controller design challenging, and to successfully overcome this challenge, two methods are proposed in this thesis. One method generates a connected model set. The idea of the multidimensional principal curves methodology is employed to detect the nonlinear correlations between parameters of the given set of system dynamics. The connected model set is simple and tight, leading to both nonconservatism and reduced computational complexity in subsequent controller design, and hence, to improve the controller performance. The other method is developed to derive a family of discrete model sets for a given set of system response data. A relaxed version of the normalized cut methodology is developed and used in an algorithm to divide a given set of system responses into the smallest possible number of partitions in such a way that a desired performance objective is satisfied for all partitions by designing one controller for each partition. Using the proposed method, a tight uncertainty model is derived for Hard Disk Drive (HDD) systems, and an H∞
controller is synthesized. The dynamics of HDDs is studied from a controller design point of view. Especially, the variations in the dynamics due to the change in temperatures and limited precision in the production line are examined. Also, the variations in the dynamics of Ball Screw Drive (BSD) systems due to the structural flexibility, runout, and workpiece mass variation are studied. These three factors are explicitly incorporated in LPV models. To build the LPV models, it is determined how the system parameters are affected by two variables, namely, the measurable table position and the uncertain mass of the table. We design robust gain scheduling controllers which are scheduled by the table position and are robust over the table mass.
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Tunstall, Glen Alan. "Dynamic characterisation of the head-media interface in hard disk drives using novel sensor systems." Thesis, University of Plymouth, 2002. http://hdl.handle.net/10026.1/1643.
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Hard disk drives function perfectly satisfactorily when used in a stable environment, but in certain applications they are subjected to shock and vibration. During the work reported in this thesis it has been found that when typical hard disk drives are subjected lo vibration, data transfer failure is found to be significant at frequencies between 440Hz and 700Hz, at an extreme, failing at only Ig of sinusoidal vibration. These failures can largely be attributed to two key components: the suspension arm and the hard disk. At non-critical frequencies of vibration the typical hard disk drive can reliably transfer data whilst subjected to as much as 45g. When transferring data to the drive controller, the drive's operations are controlled and monitored using BIOS commands. Examining the embedded error signals proved that the drive predominantly failed due lo tracking errors. Novel piezo-electric sensors have been developed to measure unobtrusively suspension arm and disk motion, the results from which show the disk to be the most significant failure mechanism, with its First mode of resonance at around 440Hz. The suspension arm movement has been found to be greatest at IkHz. Extensive modelling of the flexure of the disk, clamped and unclamped, has been undertaken using finite element analysis. The theoretical modelling strongly reinforces the empirical results presented in this thesis. If suspension arm movement is not directly coupled with disk movement then a flying height variation is created. This, together with tracking variations, leads to data transfer corruption. This has been found to occur at IkHz and 2kHz. An optical system has been developed and characterised for a novel and inexpensive flying height measurement system using compact disc player technology.
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München, Daniel Dotto. "Recuperação de neodímio a partir de ímãs de neodímio-ferro-boro por meio de processos mecânicos e hidrometalúrgicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/149837.
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O elemento químico neodímio (Nd) atualmente está em evidência pois é parte fundamental em aplicações produzidas por empresas ligadas a tecnologias limpas e de ponta. Porém, é classificado como crítico pelo departamento de energia dos EUA em função do monopólio chinês atuante em sua exploração e comercialização. Devido à crescente demanda frente à restrita disponibilidade, a recuperação deste metal está em ascensão. Uma das aplicações do neodímio é o ímã permanente de neodímio-ferro-boro, utilizado em hard disk drives (HDs) de computadores. Desta forma, este estudo visou caracterizar os ímãs provenientes de HDs de computadores e estabelecer uma rota de recuperação do neodímio por meio de processos mecânicos e hidrometalúrgicos. Por meio da pesagem dos HDs e seus ímãs obteve-se massa média de 3,04 g e 7,91 g para laptop e desktop, respectivamente, representando menos de 3% da massa total do HD. A desmagnetização foi atingida por meio de aquecimento até a temperatura de Curie, em torno de 312 °C, e a cominuição realizada em moinho de facas, onde foram obtidas três granulometrias classificadas em frações A, B e C. Qualitativamente as amostras, foram analisados por meio de difração de raios-X (DRX), onde a fase tetragonal Nd2Fe14B foi o constituinte dominante, e por meio de análise em microscópio eletrônico de varredura (MEV). Semi-quantitativamente os ímãs, seus revestimentos e o precipitado final foram avaliados por meio de espectrometria de fluorescência de raios-X (FRX). A composição média de 21,5% de neodímio e 65,1% de ferro em massa, além de outros elementos químicos, obtida por meio de espectrometria de emissão óptica com plasma (ICP-OES), mostrou teor de neodímio superior aos minérios explorados, tornando este resíduo interessante em relação à recuperação deste metal. O procedimento hidrometalúrgico adotado envolveu a lixiviação das amostras em ácido sulfúrico 2M e a variação de três parâmetros: razão sólido/líquido, temperatura e tempo, em dois níveis. Posteriormente foi realizada a precipitação seletiva por meio de NaOH, formando o duplo sal NaNd(SO4)2.nH2O. Os resultados mostraram que a lixiviação de neodímio atingiu eficiência média acima de 94%, porém todos os experimentos apresentaram material não lixiviado, majoritariamente composto por níquel e cobre.The chemical element neodymium (Nd) currently is in evidence as it is a fundamental part in applications manufactured by clean and advanced technology companies. However, it is classified as critical by the United States Department of Energy due to Chinese monopoly in its exploration and commercialization. Due to increasing demand in contrast with scarce supply, the recovery of neodymium is growing. One of the applications of this metal is the neodymium-iron-boron permanent magnet, used in hard disk drives (HDDs) of computers. Therefore, this study aimed magnets characterizing from HDDs of computers and then establishing a recovery route for neodymium by mechanical and hydrometallurgical processes. By weighing the HDDs and their magnets it was obtained the average weight of 3.04 g and 7.91 g for laptop and desktop, respectively, representing less than 3% of the HDDs total mass. Demagnetizing was achieved by heating up to Curie temperature of around 312 °C, and the comminution in knives mill resulted in three granulometries classified into fractions A, B and C. Qualitatively, magnets were analyzed by X-ray diffraction (XRD), where the tetragonal phase Nd2Fe14B was the dominant constituent of the sample, and through analysis in a scanning electron microscope (SEM). Semi-quantitatively, the magnets, its covers, and the final precipitate were evaluated by X-ray fluorescence spectrometry (XRF). The average composition of neodymium and iron showed 21.5% and 65.1% by weight, respectively, among other chemical elements. This results were obtained by optical emission spectrometry (ICP-OES), representing a higher neodymium content compared to the ores content, which makes this waste interesting from a neodymium recovery point of view. The procedure adopted involved hydrometallurgical leaching of the samples in 2M sulfuric acid varying three parameters: liquid/solid ratio, temperature and time, each one on two levels. Subsequently, the selective precipitation by NaOH was performed to form the double salt NaNd(SO4)2.nH2O. The results showed that neodymium leaching efficiency reached above 94%, but the experiments showed as well some material left, mainly composed of nickel and copper.
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Egan, Patrick W. "FePd thin films as a replacement for FePt thin films as the hard bias magnet in the read head for hard disk drives." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676287.
Full textAbstract:
The purpose of the research was commercial in that it was carried out to ascertain if the more expensive FePt thin film could be replaced by the more cost effective FePd thin film as the hard biasing magnet in the read head of a hard disk drive. Magnetron sputtering was used to deposit the thin films. The magnetic properties and crystal structure of both FePd alloy thin films and FePd multilayers were investigated using VSM, B-H Looper and XRD. Room temperature deposition together with post annealing and heated substrate deposition of both the FePd alloy and FePd multilayers was carried out. In addition the effect of seed layers, seed layer thickness and the effect of heated deposition on the grain size was also studied. The magnetic properties and crystal structure of FePd alloy thin films and the Fe/Pd multilayer thin films are affected by the deposition temperature, seed layers and seed layer thickness and also by the thickness of the Fe and Pd layers in the Fe/Pd multilayer. FePd alloy and Fe/Pd multilayer thin films were produced with in-plane magnetisation and a saturation magnetisation of 1T or better but none of the films produced have a coecivity of 3500 Oe. The 36nm Fe50Pd50 alloy film with an Bnm Ru seed layer deposited at a temperature of 450°C showed the largest He of 2500 Oe but with an Ms of only 0.79T. Therefore the FePd thin film alloy or multilayers were unable to produce the required He. FePd thin films are therefore not a viable replacement for the FePt thin films currently used as the hard biasing magnet in the read head of HDD. Similarly the temperatures used to produce the FePd films with the largest He values are too high for the read head manufacturing process, because temperatures above 350°C would cause other layers in the read head to degrade.
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Chilumbu, Chibesa. "The development of a novel suspension arm with 2-dimensional actuation, for use in advanced hard disk drives." Thesis, University of Plymouth, 2002. http://hdl.handle.net/10026.1/1626.
Full textAbstract:
As magnetic computer disks are developed to ever-greater data storage densities, the accuracy required for head positioning is moving beyond the accuracy provided by present technology using single-stage voice-coil motors in hard disk drives. This thesis details work to develop a novel active suspension arm with 2-dimensional actuation for use in advanced hard disk drives. The arm developed is capable of high-bandwidth data tracking as well as precision head flying height control motion. High-bandwidth data tracking is facilitated by the use of piezoelectric stack actuator, positioned closer to the head. The suspension arm is also capable of motion in the orthogonal axis. This motion represents active flying height control to maintain the correct altitude during drive operation. To characterise the suspension arm's structural dynamics, a high-resolution measurement system based on the optical beam deflection technique has been developed. This has enabled the accurate measurement of minute end-deflections of the suspension arm in 2-dimensions, to sub-nanometre resolution above noise. The design process of the suspension arm has led into the development of novel piezoelectric-actuated arms. In the work involving lead zirconate titanate (PZT) thick films as actuators, work in this thesis shows that reinforcing the films with fibre improves the overall actuation characteristics of the thick films. This discovery benefits applications such as structural health monitoring. The final suspension arm design has been adopted because it is simple in design, easier to integrate within current hard disk drive environment and easier to fabricate in mass. Closed-loop control algorithms based on proportional, integral and derivative (PID) controller techniques have been developed and implemented to demonstrate high bandwidths that have been achieved. The suspension arm developed presents an important solution in head-positioning technology in that it offers much higher bandwidths for data tracking and flying height control; both very essential in achieving even higher data storage densities on magnetic disks at much reduced head flying heights, compared to those in existing hard disk drives.
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Han, Younghee. "A NEW PIEZOELECTRIC MICROACTUATOR WITH TRANSVERSE AND LATERAL CONTROL OF HEAD POSITIONING SYSTEMS FOR HIGH DENSITY HARD DISK DRIVES." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_theses/349.
Full textAbstract:
In high density magnetic hard disk drives, both fast track seeking and extremely accurate positioning of the read/write head are required. A new piezoelectric microactuator with transverse and lateral control of the head positioning system for high density hard disk drives is proposed. First, the structure of the new piezoelectric microactuator is illustrated. Design of the new microactuator is based on the axial deformation of piezoelectric elements for lateral motion and the bimorph actuation of piezoelectric elements for transverse motion. Next, a mathematical model of the microactuator system is defined. Static properties associated with the displacement of the system are evaluated and then dynamic system equations of the system are evaluated. Frequency response of the system is studied based on the dynamic system equations of the actuator system. Dynamic properties of the system with a variety of system parameters are evaluated. Finally, the controller design for the actuator is presented. Simulation results show that the new actuator achieves a maximum stroke of displacement of more than 0.2m with servo bandwidth of more than 5 kHz in the lateral direction and the flying height is decreased to less than 6 nm with resonance frequency of more than 100 kHz under the 0.5 % damping assumption. The new piezoelectric microactuator improves performance of high density hard disk drives by increasing servo bandwidth and decreasing flying height.
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Gougeaud, Sebastien. "Simulation générique et contribution à l'optimisation de la robustesse des systèmes de données à large échelle." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLV011/document.
Full textAbstract:
La capacité des systèmes de stockage de données ne cesse de croître pour atteindre actuellement l’échelle de l’exaoctet, ce qui a un réel impact sur la robustesse des systèmes de stockage. En effet, plus le nombre de disques contenus dans un système est grand, plus il est probable d’y avoir une défaillance. De même, le temps de la reconstruction d’un disque est proportionnel à sa capacité. La simulation permet le test de nouveaux mécanismes dans des conditions quasi réelles et de prédire leur comportements. Open and Generic data Storage system Simulation tool (OGSSim), l’outil que nous proposons, supporte l’hétérogénéité et la taille importante des systèmes actuels. Sa décomposition modulaire permet d’entreprendre chaque technologie de stockage, schéma de placement ou modèle de calcul comme des briques pouvant être combinées entre elles pour paramétrer au mieux la simulation. La robustesse étant un paramètre critique dans ces systèmes, nous utilisons le declustered RAID pour assurer la distribution de la reconstruction des données d’un disque en cas de défaillance. Nous proposons l’algorithme Symmetric Difference of Source Sets (SD2S) qui utilise le décalage des blocs de données pour la création du schéma de placement. Le pas du décalage est issu du calcul de la proximité des ensembles de provenance logique des blocs d’un disque physique. Pour évaluer l’efficacité de SD2S, nous l’avons comparé à la méthode Crush, exemptée des réplicas. Il en résulte que la création du schéma de placement, aussi bien en mode normal qu’en mode défaillant, est plus rapide avec SD2S, et que le coût en espace mémoire est également réduit (nul en mode normal). En cas de double défaillance, SD2S assure la sauvegarde d’une partie, voire de la totalité, des donnéesCapacity of data storage systems does not cease to increase to currently reach the exabyte scale. This observation gets a real impact on storage system robustness. In fact, the more the number of disks in a system is, the greater the probability of a failure happening is. Also, the time used for a disk reconstruction is proportional to its size. Simulation is an appropriate technique to test new mechanisms in almost real conditions and predict their behavior. We propose a new software we callOpen and Generic data Storage system Simulation tool (OGSSim). It handles the heterogeneity andthe large size of these modern systems. Its modularity permits the undertaking of each storage technology, placement scheme or computation model as bricks which can be added and combined to optimally configure the simulation.Robustness is a critical issue for these systems. We use the declustered RAID to distribute the data reconstruction in case of a failure. We propose the Symmetric Difference of Source Sets (SD2S) algorithmwhich uses data block shifhting to achieve the placement scheme. The shifting offset comes from the computation of the distance between logical source sets of physical disk blocks. To evaluate the SD2S efficiency, we compared it to Crush method without replicas. It results in a faster placement scheme creation in normal and failure modes with SD2S and in a significant reduced memory space cost (null without failure). Furthermore, SD2S ensures the partial, if not total, reconstruction of data in case of multiple failures
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Chen, Lung, and 陳龍. "Taiwan's Hard Disk Drive Industry Since 1979." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/78997976227504959403.
Full textAbstract:
碩士淡江大學
國際貿易學系
86
This research describes the history of Taiwan's Hard Disk Drive Industry since 1979. After Industrial Technology Research Institute (ITRI) developed the first Hard Disk Drive, there are six major companies, including Cogito, Priam, Microscience, Magtron, Greenery and Zentek, which entered the industry during the past ten years. Somehow, they all have dropped out. Most of the previous papers regarding Taiwan's information technology alwaysProcedure passes the topic of Hard Disk Drive Industry. However, we can't deny the fact that Hard Disk Drive will be onof the most vital key components in thefuture information technology development.The research uses case-study method to find out the failing reasons of Taiwan's Hard Disk Drive industry after consulting 30 people who have been in the related area. Also, this article will show a clean and concrete picture of all those films, which have entered this field, as weexplaining why the Hard Disk Drive industry can't succeed in Taiwan. The major objective of this research includes the followings: 1. What is the institutional characteristic of global Hard Disk Driver industry? 2.The reason why Taiwan fail in the field? 3.If there is any possibility Taiwan can succeed in the industry? If yes, what can we do? : First, there are seven characteristics in Hard Disk Drive industry, including monopoly, foreign direct investment, industrial marketing, technical intensive, vertical integration, capital intensive, labor intensive. Afteyears, we can find out that all these companies which follower the above rules can survived, whereas those which against will be squeezed out.Second, the major failing reasons of Taiwan's Hard Disk Driveindustry are: 1 There leave doubt for government policy toward the development of this industry.2 There is no attraction in Taiwan for those foreign investors.3 These exist gap between films expectation and reality.4 The overall performance of domestic key component companies is below expectation.5 The quality and pricing of domestic Hard Disk Drive can't meet the needs of local PC films.6 This perception gap between companies and ITRI.7 The companies don't have a long-term vision toward R&D, so there is limited investment and innovation in products can hardly be found.8 There is no consistency and continuity in capital investment. Third, There is two ways left to be improved if Taiwan is willing to enter the market in the future:1 Start to develop key components and corporate with existing PC industry at the same time. By doing so, it should be easier to development Hard Disk Drive industry.2 Merger, like Hyundai Groups did on Maxtor, to lower therisk of entering the field as a new brand.
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Balu, Henish Hemendra. "Predicting Hard Disk Drive Failures and Misbehavior." Dissertação, 2020. https://hdl.handle.net/10216/131963.
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Balu, Henish Hemendra. "Predicting Hard Disk Drive Failures and Misbehavior." Master's thesis, 2020. https://hdl.handle.net/10216/131963.
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Huang, Peng-Yu, and 黃鵬彧. "Mining Frequent patterns under Limited Memory:Without Hard Disk Drive." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/sqfg6f.
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碩士國立高雄應用科技大學
資訊工程系
103
When it comes to data mining, it’s a noun that popped up several years ago. Nowadays, data mining has been replaced with big data mining which derives frequent pattern mining that also importantly regarded. Data has become much more important than property not only because our world is filled with computers and digital messages but also because we can't directly find what we need in a great deal of data. Thus, it's a trend to use skill-explored ways to find valuable messages and gain more benefits. According to compile statistics, because our hard disk and memory grow multiple every season results in that we can't deal with data-explored growth correct due to we only have to handle few data like 64kbyte or 128kbyte. It brings a new noun called big data mining. In this study, we come up with a way of FP-Tree. Achieving our goal by using a whole new FP-Tree and sorts an exploring of big data mining in core memory.
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Hsieh, Kun-Fang, and 謝坤芳. "Technology Strategy & New Product Development for Hard Disk Drive Head & Disk Interface : A Case of S Company Hard Disk Development." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/84767379737848156095.
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碩士國立清華大學
工業工程與工程管理學系碩士在職專班
99
Technology Strategy & New Product Development for Hard Disk Drive Head & Disk Interface: A Case of S Company Hard Disk Development Student： Kun-Fang Hsieh Advisor： Dr. Yee-Yeen Chu Department of Industrial Engineering & Engineering Management National Tsing Hua University Abstract Adopting suitable technology strategy and accelerating the new product development are critical to enhance competitiveness of corporation. This research focuses on the technology strategy for hard disk drive’s head and disk interface and the new product development of hard disk. A literature review and case study of hard disk development is conducted to analyze the technology strategy and its link with new product development, in the Design-Build-Test cycle. The research explores the ways to reduce the new product develop cycle through building up the accelerating development team in the common research lab and enhancing the communication to complete hard disk new product development. The case study uses actual participations, execution, and observations of the development practices, including deciding on technology choices, overcoming the difficulties and finding out the key factors to improve the development cycle. The research expects to provide a practical model of technology strategy and technology selection for hard disk drive’s head and disk interface. Keywords：New Product Development Technology Strategy Head Disk Interface
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Liu, Qin Zhou, and 劉欽洲. "Design of intelligent seeking controllers for hign precision hard disk drive." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/59321406574950896596.
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"Economic crisis and technological trajectories: hard disk drive production in Southeast Asia." The MIT Japan Program, Center for International Studies, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/16568.
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Rick Doner [and] Bryan Ritchie.Available in PDF from the MIT Japan Program Website.
"Date of publication: June 20, 2001"--T.p. verso. "MIT International Science and Technology Initiatives"--Cover.
Includes bibliographical references (p. 32-36).
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Song, H., Murali Damodaran, and Quock Y. Ng. "Simulation of Flow Field and Particle Trajectories in Hard Disk Drive Enclosures." 2003. http://hdl.handle.net/1721.1/3895.
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The airflow field and particle trajectories inside hard disk drive (HDD) are investigated in this study using commercial software Fluent and Gambit. Three-dimensional grids inside the HDD configuration are built using Gambit taking into account all the components and their geometric details. The airflow field inside HDD is simulated using three incompressible Navier-Stokes equations for various disk rotational speeds. The effects of using the various turbulence models inside the Fluent software such as the standard k - ε , RNG k - ε and Reynolds Stress Method on the computed airflow characteristics are also assessed. Steady flow fields and the effects of rotational speeds are assessed. Based on the computed steady airflow patterns, particle trajectories are computed using routines available in Fluent as well as special particle trajectory functions defined by the user via the user-defined functions. Particles of different sizes and materials are injected at various locations in the computed flow field and the corresponding particle trajectories are studied. Based on the investigation, the trajectory tends to be different according to sizes and materials. The present work forms a basis for further investigation of heat transfer processes inside the HDD to address thermal management issues and also the computation of unsteady flow fields in the HDD due to the movement of the actuator arm during data storage and retrievalSingapore-MIT Alliance (SMA)
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Chang, Chih-Chieh, and 張智傑. "Optimum Isolation Design for Enhancing Transmission Efficiency of a Hard Disk Drive." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/19422137213725229722.
Full textAbstract:
碩士大同大學
機械工程學系(所)
99
As hard disks continue to grow in capacity, they are becoming more and more delicate. Thus, data transfer rates are easily affected by vibration; hard disks are especially vulnerable when they are transferring data. This study places a hard disk on a vibration tester to simulate the external environment; the hard disk is put through different vibration frequencies, acceleration and angles. The hard disk is linked to a computer and how much it is affected by vibration is determined based on the data transfer rate by use IOmeter software. Taguchi methods, neural network system and genetic algorithm (GA) optimization methods are applied along with an experiment to find the optimum design for anti-shock pad hardness. This study is divided into two parts: 1. Anti-shock pad performance test: Data transfer rate is tested for anti-shock pads of different hardness, thickness and at different angles; data transfer rates are charted for when (a) only the hardness is changed, (b) only the angle is changed and (c) only the thickness is changed. 2. The frequency for when the lowest data transfer rate was measured is used as the target frequency, and then Taguchi methods, neural network system and GA is applied to find the optimum data transfer rate for a single vibration frequency. A mathematical model is constructed using neural network system based on input and output figures, and then GA is applied to find the optimum hardness of anti-shock pads, as well as the optimum data transfer rate. The resulting optimal hardness is compared with the optimal hardness calculated before conducting the experiment. According to results, for the optimum anti-shock pad hardness found using the network model created from neural network system and GA, reading speed was at least 15 IOps higher than the original reading speed. This result proves the feasibility of applying neural network system and GA in the practice of anti-shock design.
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Huang, Sheng-Shiung, and 黃聖雄. "Mining Frequent Patterns under Limited Memory: By Assistance of Hard Disk Drive." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/m9u745.
Full textAbstract:
碩士國立高雄應用科技大學
資訊工程系
103
Data mining technology has been widely studied and applied in recent years. Frequent pattern mining is one important technical field of such research. The frequent pattern mining technique is popular not only in academia but also in the business community.With advances in technology, databases have become so large that data mining is impossible because of memory restrictions. In this study, we propose a novel algorithm called Hybrid Mine (H-Mine) to help improve this situation. H-Mine saves a part of the information that is not stored in the memory, and through the use of mixed hard disk and memory mining we are able to complete data mining with limited memory. The results of empirical evaluation under various simulation conditions show that H-Mine delivers excellent performance in terms of execution efficiency and scalability.
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Lu, Szu-Wei, and 呂思緯. "Investigation of surface topography effect on drive head flying in hard disk." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ca85g8.
Full textAbstract:
碩士國立交通大學
理學院應用科技學程
106
A hard disk and a read/write head are the most important parts in a hard disk drive (HDD). With the size of an HDD getting smaller and the rotation speed of a hard disk getting higher, a few studies in the last few years have indicated that the surface morphology of a hard disk has a significant impact on head flying height and stability. Thus, for designing an HDD, we need to verify which wavelength of morphology is optimum for head flying height and use it as an index to improve the surface morphology of a hard disk. In this study, we used different conditions of polishing, annealing, sputtering and chemical etching to change the surface morphology of a hard disk. We used AE sensor (Acoustic Emission Sensor) for touch-down power measurement and optical surface analyzer (OSA) and atomic force microscopy (AFM) for measuring the surface morphology of the hard disk. Finally, we found that micro-waviness has a significant influence on the head flying height through a correlation analysis.
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Chuang, Ming-Fu, and 莊銘富. "Using RAID Technology to Sort The Performance Quality of Hard Disk Drive." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ep2as2.
Full textAbstract:
碩士輔仁大學
電機工程學系碩士在職專班
105
This paper proposes an automatic program to sort the performance quality of hard disk drive by using the Redundant Array of Independent Disks (RAID) technology with the software of IO Meter. Associating with the binary search algorithm, the disk-array configuration of RAID 5 is firstly applied to identify the groups of low-performance Logical Disk (LD). Then, using the Non-RAID (NRAID) configurations exactly recognize the unqualified hard disks. Finally, the effect of this program is confirmed at the end with the improved performance verification by replacing the problematic hard disks.