Reconstruct versus read-modify writes in RAID

Document Type

Article

Publication Date

2-28-2005

Abstract

RAID5 (Redundant Arrays of Independent Disk level 5) is a popular paradigm, which uses parity to protect against single disk failures. A major shortcoming of RAID5 is the small write penalty, i.e., the cost of updating parity when a data block is modified. Read-modify writes and reconstruct writes are alternative methods for updating small data and parity blocks. We use a queuing formulation to determine conditions under which one method outperforms the other. Our analysis shows that in the case of RAID6 and more generally disk arrays with k check disks tolerating k disk failures, RCW outperforms RMW for higher values of N and G. We note that clustered RAID and variable scope of parity protection methods favor reconstruct writes. A dynamic scheme to determine the more desirable policy based on the availability of appropriate cached blocks is proposed. © 2004 Elsevier B.V. All rights reserved.

Identifier

25444436197 (Scopus)

Publication Title

Information Processing Letters

External Full Text Location

https://doi.org/10.1016/j.ipl.2004.10.009

ISSN

00200190

First Page

163

Last Page

168

Issue

4

Volume

93

Grant

0105485

Fund Ref

National Science Foundation

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