Sparing for redundant disk arrays

Abstract

One of the main advantages of a redundant disk array architecture is that it provides fault tolerance against disk drive failures. This improvement in reliability can be further enhanced if spare drives are also added to the array since a failed drive can be expeditiously replaced. Furthermore, even though data can be reconstructed from the other drives of a redundant array in the event of a drive failure, performance is degraded substantially in this mode of operation. Clearly it is desirable to get out of this degraded mode of operation as quickly as possible. Again, having spare drives in the array will facilitate that. The purpose of this paper is to study some of the issues related to sparing in a redundant disk array. In particular, we will try to understand the effect on reliability of different sparing schemes. We will also examine the economic trade-offs of having spare drives in a system. © 1994 Kluwer Academic Publishers.