Flexible Usage of Redundancy in Disk Arrays |
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Authors: | E J Schwabe I M Sutherland |
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Affiliation: | (1) School of CTI, DePaul University, 243 S. Wabash Avenue, Chicago, IL 60604, USA eschwabe@cs.depaul.edu , US;(2) Bell Labs, Lucent Technologies, 263 Shuman Boulevard, P.O. Box 3050, Naperville, IL 60566, USA ians@research.bell-labs.com, US |
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Abstract: | It is well known that dedicating one disk's worth of space in a disk array to parity check information can allow the array
to tolerate a single failure. More recently, two possible ways of increasing that benefit through the use of additional redundant
information have been demonstrated: the additional redundancy can be used to allow the array to tolerate more than one disk
failure without the loss of information (multiple-fault
tolerance ), or it can be used to speed up the reconstruction of a single failed disk and thus reduce the impact of on-line reconstruction
on array performance (using a technique known as {parity
declustering ). However, these two advantages could not be obtained simultaneously. In this paper we demonstrate for the first time how
to divide the benefits of extra space for redundant information arbitrarily between increased fault tolerance and accelerated
reconstruction of failed disks. In addition, we give general lower bounds on the space overhead required to protect information
in a disk array by storing redundant information. These bounds widen the optimality of some known multiple-fault-tolerant
data layouts.
Received September 1997, and in final form October 1998. |
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