Efficient parity placement schemes for tolerating up to two disk failures in disk arrays

In order to achieve high reliability in disk array systems, two new schemes using dual parity placement, called DH1 (diagonal-horizontal) and DH2 sche mes, are presented. Both DH schemes can tolerate up to two disk failures by using two types of parity information placed in the diagonal and the horiz ontal directions, respectively, in a matrix of disk partitions. DH1 scheme can reduce the occurrences of the bottleneck problem significantly because the parity blocks are evenly distributed throughout the disk array. DH2 sch eme uses one more disk than DH1 scheme in order to store the horizontal par ities, while the diagonal parities are placed in the same way as in DH1 sch eme with a minor change. Even though both DH schemes use almost optimal dis k space for storing the redundant information, the encoding algorithms for them are quite simple and efficient. Moreover, both DH schemes can recover rapidly from any two disk failures. (C) 2000 Elsevier Science B.V. All righ ts reserved.