Constraint Allocation on Disks

Constraint Allocation on Disks

Phillip K.C. Tse (University of Hong Kong, China)
DOI: 10.4018/978-1-59904-225-1.ch008
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Abstract

Most existing storage servers store data stripes on magnetic hard disks. These magnetic hard disks are accessed by moving the disk heads to random disk tracks. A significant amount of overhead is spent in moving the disk heads across the disk tracks. The access time of a request would be significantly reduced if the seek time is reduced. In the normal placement of data stripes on disks being described in the two previous chapters, data stripes can be placed on any tracks with free space. There is not much consideration on the distance among data stripes of concurrent streams. Separation distances between data stripes of an object are not sufficiently constrained. Thus, the only guarantee on the upper bounds of access times is very high. Constraint allocation methods limit the available locations to store the data stripes. This helps to control the access time within media playback requirements. The data stripes are also evenly spread across the surface of the storage media. This reduces the overheads of serving concurrent streams from the same storage device. Therefore, the maximum overheads in accessing data from the storage devices, such as seek time, become lowered. In this chapter, we shall describe two constraint allocation methods that are designed for magnetic hard disks. These methods may also be applicable to other storage media that use the disk format. When many streams access the same hot object, the phase based constraint allocation supports more streams with less seek actions. We shall describe the phase based constraint allocation method in the next section. The region based allocation limits the longest seek distance among requests. After that, we describe the region based allocation method.

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Table of Contents
Foreword
Clement Leung
Acknowledgment
Chapter 1
Introduction  (pages 1-4)
Phillip K.C. Tse
This book explains the techniques to store and retrieve multimedia information in multimedia storage systems. It describes the internal architecture... Sample PDF
Introduction
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Chapter 2
Phillip K.C. Tse
To start this book, I shall first describe the characteristics of multimedia data. Then, some multimedia applications are listed. After these, I... Sample PDF
Multimedia Information
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Chapter 3
Phillip K.C. Tse
Multimedia systems are similar to traditional computer systems in terms of their architectures. Both types of systems have central processing unit... Sample PDF
Storage System Architectures
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Chapter 4
Phillip K.C. Tse
In the previous chapter, we see that the performance of a storage system depends on the amount of data being retrieved. The size of multimedia... Sample PDF
Data Compression Techniques and Standards
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Chapter 5
Phillip K.C. Tse
The access pattern on each multimedia object can have very different characteristics. Some multimedia objects are more popular and they are more... Sample PDF
Statistical Placement on Disks
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Chapter 6
Striping on Disks  (pages 101-113)
Phillip K.C. Tse
Multimedia streams need continuous data supply. The aggregate data access requirement of many multimedia streams imposes very high demand on the... Sample PDF
Striping on Disks
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Chapter 7
Phillip K.C. Tse
When extra storage space is available on the striping disks being described in the last chapter, the storage system may keep extra copies of the... Sample PDF
Replication Placement on Disks
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Chapter 8
Phillip K.C. Tse
Most existing storage servers store data stripes on magnetic hard disks. These magnetic hard disks are accessed by moving the disk heads to random... Sample PDF
Constraint Allocation on Disks
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Chapter 9
Tertiary Storage Devices  (pages 145-155)
Phillip K.C. Tse
The main objective of the tertiary storage level is to provide huge storage capacity at low cost. Several types of storage devices are available to... Sample PDF
Tertiary Storage Devices
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Chapter 10
Phillip K.C. Tse
The contiguous placement is the most common method to place traditional data files on tertiary storage devices. The storage space in the media units... Sample PDF
Contiguous Placement on Hierarchical Storage Systems
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Chapter 11
Phillip K.C. Tse
We have described the contiguous placement in the previous chapter and the statistical strategy to place objects on disks in Chapter IV. In this... Sample PDF
Statistical Placement on Hierarchical Storage Systems
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Chapter 12
Phillip K.C. Tse
The data striping technique has been successfully applied on disks to reduce the time to access objects from the disks as shown in Chapter VI.... Sample PDF
Striping on Hierarchical Storage Systems
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Chapter 13
Phillip K.C. Tse
Multimedia objects are stored on hierarchical storage systems (HSS). The objects are large in size but the access latency of HSS is high. It is... Sample PDF
Constraint Allocation on Hierarchical Storage Systems
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Chapter 14
Phillip K.C. Tse
Disk scheduling changes the sequence order to serve the requests that are waiting in the queue. While data placement reduces the access time of a... Sample PDF
Scheduling Methods for Disk Requests
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Chapter 15
Phillip K.C. Tse
Multimedia storage systems store data objects and receive streams of requests from the multimedia server. When a client wishes to display an object... Sample PDF
Feasibility Conditions of Concurrent Streams
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Chapter 16
Phillip K.C. Tse
In the previous chapter, we have presented the feasibility condition to serve request streams concurrently. In this chapter, we describe the... Sample PDF
Scheduling Methods for Request Streams
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Chapter 17
Staging Methods  (pages 263-271)
Phillip K.C. Tse
When data are stored in the tertiary storage devices, the tape drives shall read them from the tapes using the input/output (I/O) operations. Due to... Sample PDF
Staging Methods
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Chapter 18
Time Slicing Method  (pages 272-279)
Phillip K.C. Tse
Tertiary storage devices provide huge storage capacity at low cost. Multimedia objects stored on the tertiary storage devices are accessed with high... Sample PDF
Time Slicing Method
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Chapter 19
Normal Pipelining  (pages 280-288)
Phillip K.C. Tse
Multimedia objects can be stored on tertiary storage devices to provide large storage capacity at low cost. The staging method retrieves the whole... Sample PDF
Normal Pipelining
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Chapter 20
Phillip K.C. Tse
Multimedia objects that are stored on tertiary storage devices enjoy the large storage capacity at low cost. These objects may be retrieved using... Sample PDF
Space Efficient Pipelining
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Chapter 21
Segmented Pipelining  (pages 299-319)
Phillip K.C. Tse
The robotic tape library and optical jukebox provide huge and cheap capacity for the storage of multimedia objects. The stored objects may be... Sample PDF
Segmented Pipelining
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Chapter 22
Memory Caching Methods  (pages 325-340)
Phillip K.C. Tse
The objective of data caching and object caching is to improve the performance in accessing multimedia objects from their storage. An efficient... Sample PDF
Memory Caching Methods
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Chapter 23
Stream Dependent Caching  (pages 341-367)
Phillip K.C. Tse
Caching has been successfully implemented on the Internet to reduce workload on the content server and the Internet. We have seen in the last... Sample PDF
Stream Dependent Caching
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Chapter 24
Cooperative Web Caching  (pages 368-382)
Phillip K.C. Tse
Most clients are placed behind the proxy servers on the Internet. Proxy servers have the disk cache space, network bandwidth, and availability to... Sample PDF
Cooperative Web Caching
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About the Author