An analytical model of reconstruction time in mirrored disks

Abstract

While data replication has been widely used as a means of increasing the data availability and system reliability for critical applications, we still lack a good analytical model of the recovery process after disk failure. In this paper, we present a detailed and accurate model of the reconstruction process which takes into account the disk characteristics as well as the differing characteristics of external accesses and reconstruction reads. A functional equation is derived to represent the delay faced by reconstruction reads, and a solution is given. External access delays are found based on this. Approximate closed form solutions are derived, and are shown by numerical comparison to be very accurate. © 1994.