• Title, Summary, Keyword: Disk Block

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A Bitmap-based Continuous Block Allocation Scheme for Realtime Retrieval Service (실시간 재생 서비스를 위한 비트맵 방식의 연속 블록 할당 기법)

  • 박기현
    • Journal of Korea Multimedia Society
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    • v.5 no.3
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    • pp.316-322
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    • 2002
  • In this paper we consider continuous block allocation scheme of UNIX file system to support real time retrieval service. The proposed block allocation scheme is designed to place real time data at appropriate disk block location in considering the consume-rate that is given with real time data. To effectively determine the disk block location we analyze the relationship between consume-rate and the two variable factors that are the number of continuous blocks and the cylinder distance of logically consecutive data. In traditional UNIX block allocation scheme it is in fact impossible to find continuous free disk blocks in a specific cylinder location. Thus we propose new bitmap-based free block allocation scheme that enables to determine whether a block in specific cylinder location is free state, or not.

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An Efficient Algorithm for Restriction on Duplication Caching between Buffer and Disk Caches (버퍼와 디스크 캐시 사이의 중복 캐싱을 제한하는 효율적인 알고리즘)

  • Jung, Soo-Mok
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.10 no.1
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    • pp.95-105
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    • 2006
  • The speed of hard disk which is based on mechanical operation is more slow than processor. The growth of processor speed is rapid by semiconductor technology, but the growth of disk speed which is based on mechanical operation is not enough. Buffer cache in main memory and disk cache in disk controller have been used in computer system to solve the speed gap between processor and I/O subsystem. In this paper, an efficient buffer cache and disk cache management scheme was proposed to restrict duplicated disk block between buffer cache and disk cache. The performance of the proposed algorithm was evaluated by simulation.

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A Block Replacement Scheme using Analytic Hierarchy Process in Hybrid HDD (하이브리드 하드디스크에서 AHP를 적용한 블록 교체 기법)

  • Kim, Jeong-Won
    • Journal of the Korea Industrial Information Systems Research
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    • v.20 no.5
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    • pp.45-52
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    • 2015
  • The read performance of hybrid hard disk is better than the legacy hard disk and power consumption is also considerably low. As blocks with enough localities may be located in the non-volatile cache whose size is generally limited, an effective block replacement scheme is required. As this replacement is inevitably affected by various parameters, we define this issue as a kind of multiple criteria decision model. To solve this problem, this paper suggests a new block replacement algorithm based on the analytic hierarchy process. Through simulation for our model, we confirmed that the proposed model could be used as a replacement algorithm of the hybrid hard disk as it may improve boot time as well as response time of general applications.

The Numerical Simulation of the Airflow for Reducing Vibrations of an Actuator in HDDs (하드디스크 드라이브 내부 유동에 의한 액추에이터의 진동 저감을 위한 수치해석 연구)

  • Park, Jae-Hyun;Yoo, Jin-Gyoo;Rhim, Yoon-Chul
    • Proceedings of the KSME Conference
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    • pp.664-669
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    • 2003
  • Recently, the recording density of hard disk drives has improved at an annual percentage rate of 100%. Therefore for faster access, higher disk rotational speeds will be required. The influence of the airflow produced by the rotation of a disk on the positioning accuracy has become a serious topic of research and the aerodynamic aspect of hard disk drives is now quite considerable with the increases in recording density and higher rotational speeds. Unsteady airflow in an actual hard disk drive is numerically simulated by using LES(Large Eddy Simulation) technique, we could predicted and aerodynamic mechanism that was related actuators' surroundings in HDD. At a result, with modifying the various shapes of the E-block and Damper, we estimated the characteristic of the influence of airflow in HDDs.

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Performance Evaluation of Disk I/O for Web Proxy Servers (웹 프락시 서버의 디스크 I/O 성능 평가)

  • Shim Jong-Ik
    • The KIPS Transactions:PartC
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    • v.12C no.4
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    • pp.603-608
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    • 2005
  • Disk I/O is a major performance bottleneck of web proxy server. Today's most web proxy sowers are design to run on top of a general purpose file system. But general purpose file system can not efficiently handle web cache workload, small files, leading to the performance degradation of entire web proxy servers. In this paper we evaluate the performance potential of raw disk to reduce disk I/O overhead of web proxy servers. To show the performance potential of raw disk, we design a storage management system called Block-structured Storage Management System (BSMS). And we also actually implement web proxy server that incorporate BSMS in Squid. Comprehensive experimental evaluations show that raw disk can be a good solution to improve disk I/O performance significantly for web proxy servers.

Effects on TMR and Airflow in HDD Cavity due to Disk Damper Shapes (디스크 댐퍼 형상이 HDD 내부 유동 및 TMR에 미치는 영향)

  • Um Yo-Han;Rhim Yoon-Chul
    • 정보저장시스템학회:학술대회논문집
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    • pp.248-253
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    • 2005
  • The recording density of a hard disk drive is increasing so rapidly that the storage capacity of a commercial HDD in PC reaches several hundred giga bytes recently. Many technologies related to the HDD, such as servo, media, actuator dynamics, thermo and fluid dynamics, etc. must be developed together to realize high recording density. Especially, researches in the airflow inside the HDD cavity become important as the rotational speed of a disk increases. Typical problem due to the airflow is the vibration of an actuator as the airflow collides with an I-block, suspensions and sliders, that is, FIV(Flow Induced Vibration). This problem is one of the significant sources of increasing TMR so that it must be resolved. In this research, a disk damper shape has been modified to minimize the effects of airflow on the actuator. Modified disk dampers which change flow field inside HDD cavity show good effects not only on the disk (tufter but also on the vibration of an actuator. Vibrations of E- block and slider have been measured with LDV and the airflow field inside the HDD cavity has been analyzed using a commercial package to verify these effects.

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Effects on TMR and Airflow in HDD Cavity due to Disk Damper Shapes (디스크 댐퍼 현상이 HDD 내부 유동 및 TMR에 미치는 영향)

  • Um, Yo-Han;Rhim, Yoon-Chul
    • Transactions of the Society of Information Storage Systems
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    • v.2 no.1
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    • pp.32-37
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    • 2006
  • The recording density of a hard disk drive(HDD) has been increased so rapidly that the storage capacity of a commercial HDD for the personal computer already reaches several hundred giga-bytes recently. Many technologies related to the HDD, such as servo, media, actuator dynamics, thermo and fluid dynamics, etc. must be developed together to realize higher recording density. Especially, airflow inside the HDD cavity has been concerned as the rotational speed of the disk increases. Typical problem due to the airflow is the off-track vibration of a head stack assembly(HSA) as the airflow collides with the E-block, suspensions, and sliders, i.e., the flow induced vibration(FIV). This problem is one of the most significant sources of the track mis-registration(TMR) so that it must be resolved. In this study, disk damper shape is modified to minimize the influence of airflow on the HSA. Modified disk dampers, which change the flow field of the inside cavity of a HDD, show good effects not only on the disk vibration but also on the off-track vibration of a HSA. Vibrations of E-block and slider have been measured with LDV and the airflow field inside the HDD cavity has been analyzed with commercial CFD program to verify these effects.

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On the study of block replacement policy using LFR (LFR기법을 이용한 블럭교체 기법에 관한 연구)

  • 오재환;김상수김미선
    • Proceedings of the IEEK Conference
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    • pp.499-502
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    • 1998
  • Most popular disk block replacement polices are LRU(Least Recently Used)policy and LFU(Least Frequently Used)policy. The LRU policy replaces blocks according to the most recent reference without considering the frequency of reference. The LFU policy replaces blocks according to the frequency of reference without considering the recently of the reference. In this thesis, a policy called LFR(least Frequently Use & Not Used Recently) disk block replacement policy is presented. The LFR policy subsumes the LFU policy and the NUR policy. The spectrum of the LFR policy exists between the LFU policy and the NUR policy because we co give different weight to each reference of a block. The implementation shows LFR policy outperforms the previously implemente LRU policy.

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Using Outermost-Zone Tracks as a Cache to Boost Disk Write Performance (디스크 쓰기 성능 향상을 위한 가장자리 영역 트랙의 이용)

  • U, Jong-Jeong;Hong, Chun-Pyo
    • The Transactions of the Korea Information Processing Society
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    • v.6 no.11
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    • pp.3116-3123
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    • 1999
  • Current disk systems are generally designed to reduce read traffic more effectively. Hence, write traffic of the I/O workload could potentially become a bottleneck of the disk system performance. In order to overcome this problem without much cost, this paper presents using outermost-zone track of multi-zoned recording disk as a secondary disk cache. The proposed disk cache improves the disk system performance by following exploitations: speed difference between block transfer and track transfer, difference in transfer rate between outermost-zone tracks and inner tracks, reduction in the seek time caused by decreasing the number of disk cache tracks, and idle period during burst accesses. In addition, it does not waste the disk space because it allocates the caching space by the cylinder unit. The simulation results show that the proposed system improves 2.54∼3.11 times better in terms of average response time for write operations than existing disk systems..

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An Efficient Data Block Replacement and Rearrangement Technique for Hybrid Hard Disk Drive (하이브리드 하드디스크를 위한 효율적인 데이터 블록 교체 및 재배치 기법)

  • Park, Kwang-Hee;Lee, Geun-Hyung;Kim, Deok-Hwan
    • Journal of KIISE:Computing Practices and Letters
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    • v.16 no.1
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    • pp.1-10
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    • 2010
  • Recently heterogeneous storage system such as hybrid hard disk drive (H-HDD) combining flash memory and magnetic disk is launched, according as the read performance of NAND flash memory is enhanced as similar to that of hard disk drive (HDD) and the power consumption of NAND flash memory is reduced less than that of HDD. However, the read and write operations of NAND flash memory are slower than those of rotational disk. Besides, serious overheads are incurred on CPU and main memory in the case that intensive write requests to flash memory are repeatedly occurred. In this paper, we propose the Least Frequently Used-Hot scheme that replaces the data blocks whose reference frequency of read operation is low and update frequency of write operation is high, and the data flushing scheme that rearranges the data blocks into the multi-zone of the rotation disk. Experimental results show that the execution time of the proposed method is 38% faster than those of conventional LRU and LFU block replacement schemes in I/O performance aspect and the proposed method increases the life span of Non-Volatile Cache 40% higher than those of conventional LRU, LFU, FIFO block replacement schemes.