Mirrored disk organization reliability analysis

Document Type

Article

Publication Date

12-1-2006

Abstract

Disk mirroring or RAID level 1 (RAID1) is a popular paradigm to achieve fault tolerance and a higher disk access bandwidth for read requests. We consider four RAID1 organizations: basic mirroring, group rotate declustering, interleaved declustering, and chained declustering, where the last three organizations attain a more balanced load than basic mirroring when disk failures occur. We first obtain the number of configurations, A(n, i), which do not result in data loss when i out of n disks have failed. The probability of no data loss in this case is A(n, i)/(n/i). The reliability of each RAID1 organization is the summation over 1 ≤ i ≤ n/2 of A(n, i)rn-i(1 - r)i, where r denotes the reliability of each disk. A closed-form expression for A(n, i) is obtained easily for the first three organizations. We present a relatively simple derivation of the expression for A(n, i) for the chained declustering method, which includes a correctness proof. We also discuss the routing of read requests to balance disk loads, especially when there are disk failures, to maximize the attainable throughput. © 2006 IEEE.

Identifier

33947271266 (Scopus)

Publication Title

IEEE Transactions on Computers

External Full Text Location

https://doi.org/10.1109/TC.2006.201

ISSN

00189340

First Page

1640

Last Page

1644

Issue

12

Volume

55

Grant

0105484

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