Publication Type

Journal Article

Version

acceptedVersion

Publication Date

11-1997

Abstract

Multimedia applications that are required to manipulate large collections of objects are becoming increasingly common. Moreover, the size of multimedia objects, which are already huge, are getting even bigger as the resolution of output devices improve. As a result, many multimedia storage systems are not likely to be able to keep all of their objects disk-resident. Instead, a majority of the less popular objects have to be off-loaded to tertiary storage to keep costs down. The speed at which objects can be accessed from tertiary storage is thus an important consideration. In this paper, we propose an adaptive data retrieval algorithm that employs a combination of staging and direct access in servicing tertiary storage retrieval requests. At retrieval time, an object that resides in tertiary storage can either be staged to and then played back from disks, or the object can be accessed directly from the tertiary drives. We show that a simplistic policy that adheres strictly to staging or direct access does not exploit the full retrieval capacity of both the tertiary library and the secondary storage. To overcome the problem, we propose a data retrieval algorithm that dynamically chooses between staging and direct access, based on the relative load on the tertiary versus secondary devices. A series of simulation experiments confirms that the algorithm achieves good access times over a wide range of workloads and resource configurations. Moreover, the algorithm is very responsive to changing load conditions.

Keywords

Data migration, Feedback control, Multimedia server, Storage hierarchy, Tertiary library

Discipline

Databases and Information Systems

Publication

Multimedia Systems

Volume

5

Issue

6

First Page

386

Last Page

399

ISSN

0942-4962

Identifier

10.1007/s005300050070

Publisher

Springer Verlag

Additional URL

https://doi.org/10.1007/s005300050070

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