• Title/Summary/Keyword: disk scheduling

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Transaction Scheduling Technique Using Doible Locking in a Soft Real-Time Databaes System (소프트 실시간 데이타베이스 시스템에서 이중 록킹을 이용한 트랜잭션 스케쥴링 기법)

  • Choi, Eui-In;Go, Byeong-O
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.3
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    • pp.639-648
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    • 1997
  • As the areas of computer application are expanded, the real-time applicition enviroments that must process as many transactions as possible within their deadlines have been increased recently. Conventional disk based databaes system is not appropriate in real-time transaction processing due to delying time for disk I/O processing. When the system is overloaede, the performance of transaction scheduling technique using earliest deadline first deteriorates rapidly because it can assign the highest priority ot a transaction that has already missed or is about to miss tis deadline. Therfore, the performance of suggested transaction secheduling technique is made to improved by propos-ing the doule locking mechanism based on priority. Finally, in order to evaluate the performance of the proposed priority-based double locking techniques under single proessor and main memory database system environments, the simulation model was developed using the SLAM II language.

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A Request Scheduling Strategy using Client's Buffer in VOD Systmes (주문형 비디오 시스템에서 클라이언트 버퍼를 활용한 요구 스케쥴링 기법)

  • Han, Kum-Hee;Kim, Jong-Hoon;Won, Yoo-Hun
    • The Transactions of the Korea Information Processing Society
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    • v.7 no.2
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    • pp.337-346
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    • 2000
  • In a Vod(video0on-demand) system, a scheduling strategy is designed to increase the system efficiency and to eatisfy the isochronous requirements of showing a video to multiple viewers with one disk access. In this paper, we have proposed the Stream Relay Scheme (SRS) which utilizes the client's buffer space to reduce the server's disk I/O, buffer consumption, and stream capacity. Under the SRS which we have proposed in this paper, the server does not service all the requests directly but forwards the new request selectively to the client who is being served currently in order to reduce the initial latency and increase the system throughput. The SRS-BAT which integrated the SRS with the Batching technique is introduced. The results of the simulated experiments which compared the SRS with the conventional technique have shown the noticeable performance improvements in terms of initial latency and the server throughput.

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The Node Scheduling of Multi-Threaded Process for CC-NUMA System (CC-NUMA 시스템을 위한 다중 스레드 프로세스의 노드 스케줄링 설계 및 구현)

  • Kim, Jeong-Nyeo;Kim, Hae-Jin;Lee, Cheol-Hoon
    • The Transactions of the Korea Information Processing Society
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    • v.7 no.2
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    • pp.488-496
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    • 2000
  • this paper describes the design and implementation of node scheduling for MX Server that is CC-NUMA System COMSIX, the operating system of MX Server, is designed to suit for CC-NUMA Architecture. MX Server consists of up to 8 nodes, and each node is connected by SCI ring. This node scheduling scheme considers data locality for performance improvement of Oracle8i DBMS on the CC-NUMA architecture. For DBMS such as Oracle8i, a multi-threaded process may be run to tie on particular disk. We have developed a CG binding function that the multi-threaded process bound the node. Currently, We don't have an available CC-NUMA Platform. Instead of MX Server, we developed the Node scheduling scheme for multi-threaded process to suit server platform on the PC test-bed and tested completely.

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An Effective Video Block Placement Strategy on VOD Storage Server with MZR Disks (MZR 디스크를 채택한 VOD 저장서버의 효율적인 비디오 블록 배치방법)

  • Lim, Hyoung-Roung;Kim, Jeong-Won;Kim, Young-Ju;Chung, Ki-Dong
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.12
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    • pp.2971-2984
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    • 1997
  • In this paper, we propose an efficient video block Placement scheme that utilize the current disk product that has MZR disk characteristic and users' skewed access pattern on VOD. Also, we evaluate its performance through simulation and modeling of VOD server. The basic placement rule is to place on MZR disks by LP, SHP methods according to the Zipf distribution of popularity. To verify the proposed scheme, we examined its performance on workstation with 2 MZR disks under varied skewed factors. The proposed placement scheme showed better response time than the random method. To extend proposed placement scheme to disk group, we analyzed the theoretical maximum numbers of concurrent users and the required buffer size per user. For performance parameters for the proposed scheme, we considered the disk head scheduling methods, the placement methods and the striping unit. The result of experiments showed that the proposed scheme was effective.

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Design of a Vido Storage Server that Maximizes Concurrent Streams and Minimizes Initial Latency (사용자 수 증대와 초기 대기시간 감소를 위한 비디오 저장 서버의 설계)

  • Ma, Pyeong-Su;Jo, Chang-Sik;Jin, Yun-Suk;Sin, Gyu-Sang
    • The Transactions of the Korea Information Processing Society
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    • v.6 no.10
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    • pp.2608-2617
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    • 1999
  • One of the most important functionality that commercial video storage servers should provide is to maximize the number of concurrent streams and to minimize the initial latency of new requests. In this paper, we propose a data placement scheme whose disk read unit size can be twice large than that of conventional striping methods. The proposed scheme can significantly increase the number of concurrent streams, since the ratio of rotational latency time is decreased and the disks are effectively utilized. The disk scheduling scheme we propose guarantees constant initial latency time. We also propose a procedural design method for a storage server by introducing the concept of allowed initial latency. The comparison with previous research shows that the proposed scheme provides better performance.

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Range Query Processing of Distributed Moving Object Databases using Scheduling Technique (스케쥴링 기법을 이용한 분산 이동 객체 데이타베이스의 범위 질의 처리)

  • Jeon, Se-Gil;Hwang, Jae-Il;Nah, Youn-Mook
    • Journal of Korea Spatial Information System Society
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    • v.6 no.2 s.12
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    • pp.51-62
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    • 2004
  • Recently, the location-based service for moving customers is becoming one of the most important service in mobile communication area. For moving object applications, there are lots of update operations and such update loads are concentrated on some particular area unevenly. The primary processing of LBS application is spatio-temporal range queries. To improve the throughput of spatio-temporal range queries, the time of disk I/O in query processing should be reduced. In this paper, we adopt non-uniform two-level grid index structures of GALIS architecture,which are designed to minimize update operations. We propose query scheduling technique using spatial relationship and time relationship and a combined spatio-temporal query processing method using time zone concepts to improve the throughput of query processing. Some experimental results are shown for range queries with different query range to show the performance tradeoffs of the proposed methods.

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Parallelism-aware Request Scheduling for MEMS-based Storages (MEMS 기반 저장장치를 위한 병렬성 기반 스케줄링 기법)

  • Lee, So-Yoon;Bahn, Hyo-Kyung;Noh, Sam-H.
    • Journal of KIISE:Computer Systems and Theory
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    • v.34 no.2
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    • pp.49-56
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    • 2007
  • MEMS-based storage is being developed as a new storage media. Due to its attractive features such as high-bandwidth, low-power consumption, high-density, and low cost, MEMS storage is anticipated to be used for a wide range of applications from storage for small handhold devices to high capacity mass storage servers. However, MEMS storage has vastly different physical characteristics compared to a traditional disk. First, MEMS storage has thousands of heads that can be activated simultaneously. Second, the media of MEMS storage is a square structure which is different from the platter structure of disks. This paper presents a new request scheduling algorithm for MEMS storage that makes use of the aforementioned characteristics. This new algorithm considers the parallelism of MEMS storage as well as the seek time of requests on the two dimensional square structure. We then extend this algorithm to consider the aging factor so that starvation resistance is improved. Simulation studies show that the proposed algorithms improve the performance of MEMS storage by up to 39.2% in terms of the average response time and 62.4% in terms of starvation resistance compared to the widely acknowledged SPTF (Shortest Positioning Time First) algorithm.

Enhanced NOW-Sort on a PC Cluster with a Low-Speed Network (저속 네트웍 PC 클러스터상에서 NOW-Sort의 성능향상)

  • Kim, Ji-Hyoung;Kim, Dong-Seung
    • Journal of KIISE:Computer Systems and Theory
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    • v.29 no.10
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    • pp.550-560
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    • 2002
  • External sort on cluster computers requires not only fast internal sorting computation but also careful scheduling of disk input and output and interprocessor communication through networks. This is because the overall time for the execution is determined by reflecting the times for all the jobs involved, and the portion for interprocessor communication and disk I/O operations is significant. In this paper, we improve the sorting performance (sorting throughput) on a cluster of PCs with a low-speed network by developing a new algorithm that enables even distribution of load among processors, and optimizes the disk read and write operations with other computation/communication activities during the sort. Experimental results support the effectiveness of the algorithm. We observe the algorithm reduces the sort time by 45% compared to the previous NOW-sort[1], and provides more scalability in the expansion of the computing nodes of the cluster as well.

Holographic disk memories based on localized hologram recording (국소 홀로그램 기록방식에 기초한 홀로그래픽 디스크 메모리)

  • 오용석;김복수;장주석;강영수
    • Korean Journal of Optics and Photonics
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    • v.14 no.6
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    • pp.663-668
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    • 2003
  • We studied a localized hologram recording method that can be used in a disk-shaped medium. In this method, the reference beam is focused by use of a cylindrical lens to get a thin spot in the medium, and then a hologram is recorded in that spot by illuminating the signal beam. Many localized holograms are multiplexed by shifting the medium by a distance more than the thin spot size of the reference beam. This method does not need recording-time scheduling for uniform diffraction efficiencies. We show that a minimal required thickness of the recording medium exists for a given spot size of the signal beam. We performed experiments for data storage and retrieval, and obtained a storage density of 20 bits/${\mu}{\textrm}{m}$$^2$ and a raw-bit error rate (RBER) of 2.5${\times}$10$^{-3}$ , when a 2 mm-thick Fe-doped LiNbO$_3$ crystal was used.

A Tradeoff Scheme Between Disk Bandwidth and Buffer Allocation for VBR Data Scheduling (가변 비트율 데이터 스케줄링을 위한 디스크 대역폭과 버퍼 할당의 Tradeoff 기법)

  • 김인환;김정원;정기동
    • Proceedings of the Korean Information Science Society Conference
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    • 1998.10a
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    • pp.36-38
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    • 1998
  • 비디오 서버에서 가변 비트율 데이터를 위한 다양한 스케줄링 기법이 제안되어 왔다. 가변 비트율로 저장장치에 저장된 비디오 데이터를 재생할 때 최악의 경우를 가정하여 디스크 대역폭을 할당하면 디스크 대역폭 이용율이 매우 낮아진다. 디스크 대역폭의 이용율을 높이기 위한 방법으로 선반입 기법을 사용하는데 이를 위해서는 많은 버퍼가 필요하다. 본 논문에서는 가변 비트율 데이터를 위한 윈도우별 선반입에 기반한 데이터 스케줄링에서 시스템의 자원 상황을 고려하여 적절한 디스크 대역폭과 버퍼 할당을 Tradeoff 하는 기법을 제안한다. 제안한 기법은 비디오 데이터에 대한 메타 데이터를 미리 구축하고 이에 따라 자원을 윈도우 단위로 할당한다. 선반입은 윈도우 단위로 실시하며 선반입에 필요한 버퍼가 과다하게 증가하는 것을 조절한다. 모의 실험에서는 기존의 가변 비트율 데이터 스케줄링 기법과 제안한 기법의 자원 할당량과 동시 지원 가능 사용자수를 실험하고 비교하였다.

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