• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1056-1061
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• 2000

Particles existing in a hard disk drive are known as a major source of TA(thermal asperity). Researchers have investigated how particles induce the TA phenomena, but have not verified yet the reason why and how particles are generated in a HDD. The objective of this study is to investigate why and how particles are generated, and in what condition, the largest number of particles is generated. The number of particles generated in a HDD was measured over the landing zone after various rest times of slider and during various motions and positions of slider. It is found that the large number of particles was generated when the HDD was turned on after a long rest time of slider and that a few of particles were continuously generated when the slider flied over the disk surface. It is thought that the number of particles generated in a HDD was related to the rest time of slider because the rest time of slider increased stiction, and that there were intermittent contacts between the slider and the disk surface when the slider flied over the disk surface.

• Tribology and Lubricants
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• v.16 no.6
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• pp.415-424
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• 2000

The use of magnetoresistive (MR) head requires much tighter control of particle contamination in a drive since loose particles on the disk surface will generate thermal asperities (TA). In this study, a spinoff test was performed to investigate the adhesion and removal capability of a particle to disk surface. Numerical simulation was also performed to investigate dominant factor of particle detachment and to support experimental results. It was shown that particles are detached from the disk surface by the moment derived from the centrifugal force and the drag force and that the centrifugal force and capillary force are the dominant force, which determines spin-off of a particle on the disk surface. Removal of particles smaller than several micrometers, which are the main source of TA generation, is extremely difficult since the adhesion forces exceed the centrifugal force. Lubricant types and manufacturing process also influence the particle removal. Lower bonding ratio and lower viscosity of the lubricant will help to increase the removal rate of the particles from the disk surface.

• Tribology and Lubricants
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• v.19 no.2
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• pp.102-108
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• 2003

The height of laser bumps has been considered as the limit of the minimum flying height in the contact start-stop (CSS) of hard disk drives. In this paper, tribological interactions at flying height under laser bumps are investigated in a spin stand for development of ultra-low flying head-disk interface. With the reduction of the spinning speed in a spin stand, the flying height is decreased under the height of laser bumps and, then, head-disk interactions are investigated using AE and stiction/friction signals. During seek tests and 20000 cycle-sweep tests, AE and stiction/friction signals are not significantly changed and there are no catastrophic failures of head-disk interface. Bearing analysis and AFM analysis show that there are signs of wear and plastic deformation on the disks. It is suggested that flying height could be as low as and, sometimes, lower than laser bump height.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.1
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• pp.15-22
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• 2017

Although there are many efficient techniques to minimize the speed gap between processor and the memory, it remains a bottleneck for various commercial implementations. Since secondary memory technologies are much slower than main memory, it is challenging to match memory speed to the processor. Usually, hard disk drives include semiconductor caches to improve their performance. A hit in the disk cache eliminates the mechanical seek time and rotational latency. To further improve performance a divided disk cache, subdivided between metadata and data, has been proposed previously. We propose a new algorithm to apply the SSD that is flash memory-based solid state drive by applying FTL. First, this paper evaluates the performance of such a disk cache via simulations using DiskSim. Then, we perform an experiment to evaluate the performance of the proposed algorithm.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.303-309
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• 1999

Optimum tribological performance of the head/disk system is critical in maintaining reliable data processing in a hard disk drive. Particularly, as the flying height of the slider continues to decrease with increasing recording density, frictional interaction between the slider and the disk need to be better understood. In this work the effect of reduced ambient pressure on the tribological behavior of the head/disk interface is presented. It is found that surface damage of the components can be accelerated by reducing the ambient pressure. This method may be utilized to assess slider/disk compatibility of newly developed systems in short time.

• Transactions of the Society of Information Storage Systems
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• v.3 no.2
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• pp.81-85
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• 2007

Reliability of a hard disk drive depends on the head disk interface (HDI) characteristics. Particularly, the disk media and the head can be damaged due to contact between the two components during operation. The contact may occur due to particles being introduced into the disk/slider interface or due to direct contact between the slider and the disk. Such contacts may be induced by external vibration or abnormal operation of the HDI. In this work the characteristics of scratches generated on the disk surface were investigated. The scratches were generated by impacting the hard disk. The type of scratches was analyzed with respect to their shape and dimensions.

• Tribology and Lubricants
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• v.17 no.4
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• pp.312-320
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• 2001

In magnetic hard disk drives, higher areal recording density requires reduction of head-disk spacing. To overcome the increase of stiction associated with reduction of head-disk spacing, a padder slider, which adds pads to slider's air bearing surface, can be one of the practical solution for sub 20 nm flying height, and even for near contact recording. This study investigated the tribological characteristics of a padder slider. A padder slider took off slowly but showed less friction force than a normal slider. The hot/dry CSS test and drag test indicated that pad wear of a padder slider was negligible. The tribological performance of disk is an important factor to be considered. In particular, less carbon overcoat layer of the disk will result in higher stiction and wear in slider/disk interface. In conclusion, a padder slider shows encouraging tribological performances for practical use in HDD.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.3
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• pp.43-52
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• 2007

A hard disk, which can be classified as an external storage is usually capacious and economical. In spite of the attractive characteristics and efforts on the performance improvement, however, the operation of the hard disk is apparently slower than a processor and the advancement has also been slowly conducted since it is based on mechanical process. On the other hand, the advancement of the processor has been drastically performed as semiconductor technology does. So, disk I/O sub-system becomes bottleneck of computer systems' performance. For this reason, the research on disk I/O sub-system is in progress to improve computer systems' performance. In this paper, we proposed multi-level LRU scheme and then apply it to the computer systems with buffer cache and disk cache. By applying the proposed scheme to computer systems, the average access time to disk blocks can be decreased. The efficiency of the proposed algorithm was verified by simulation results.

• Transactions of the Society of Information Storage Systems
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• v.3 no.2
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• pp.66-72
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• 2007

Surface finishing using magnetorheological (MR) fluid is useful to finish small but not too small workpieces such as those in a few millimeter scale. However, due to the high surface hardness, this finishing process does not seem to be suit for applying to a hard disk slider. In this work, a preliminary study is performed on the finishing of the hard disk slider surface with a mixture of an MR fluid and diamond powder. During a wheel type MR finishing process, centrifugal force is found to be a major factor to cause a reduction in material remove rate (MRR), which is supported by a theoretical model. To facilitate this founding, the rotational speed of tool is confined to 500rpm while a rectilinear alternating motion with the mean speed, which is equivalent to the rotational speed, is additionally applied to the workpieces. As a consequence, MRR of about 2 times of the sole rotational case is obtained. This paper shows that MR finishing process can be used to polish a hard material in millimeter scale efficiently by controlling the speeds of the tool and the workpiece.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.45-50
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• 1997

In recent years the recording density of hard disk has been increasing largely due to the decreasing flying height of head. However, as the flying height is decreased the reliability issue becomes ever more critical. This is because the reliability and durability of hard disk is related to the head/disk interaction as the two components come into partial or full contact. In this work characteristics of friction and stiction in head/disk interface was investigated using constant speed drag test and CSS(contact-start-stop) test. The purpose of this research is to identify the frictional properties of head/disk interface