Using shared parity disks to improve the reliability of RAID arrays

Abstract

Abstract-We propose to increase the reliability of RAID level 5 arrays used for storing archival data. First, we identify groups of two or three identical RAID arrays. Second, we add to each group a shared parity disk containing the diagonal parities of their arrays. We show that the new organization can tolerate all double disk failures and between 75 and 89 percent of triple disk failures without incurring any data loss. As a result, the additional parity disk increases the mean time to data loss of the arrays in the group it protects by at least 14,000 percent.

Low-Complexity Array Codes for Random and Clustered 4-Erasures

“…There have been prior attempts to improve the implementation efficiency of array codes by departing from the requirement to correct all possible 4-erasures [7], [11]. However, these attempts used "black-box" compositions of known codes, which result in poor clustered and random erasure correctability, compared to the results of this paper.…”

Computing the Probability for Data Loss in Two-Dimensional Parity RAIDs

“…The solution to this problem is a requirement for computing the overall data loss probability using, for example, the model by Hafner and Rao [11]. This model has been applied in the past [2], [4], [5] to solve the problem for specific RAID schemes, but only for a limited number of disk failures.…”