Flexible usage of parity storage space in disk arrays
Eric J. Schwabe, Ian M. Sutherland · 1996
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 space for parity check information have been demonstrated: The additional space can be used to allow the array to tolerate more than one disk faihtre 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 par-it~declus tering).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 parity check information arbitrarily between increased fault tolerance and accelerated reconstruction of failed disks.In addition, we give a general lower bound on the space overhead required to protect information in a disk array by storing redundant information that widens the optimality of some known multiple-faulttolerant data layouts.