Abstract: A method and apparatus for sharing distributed spares of a first array with a second array in a storage subsystem which included a number of storage arrays requires that at least a first array of the subsystem has available distributed spares, and that at least a second array has a same number of "rows" as the first array, for spare sharing. When a device failure occurs on the second array, the data and parity blocks of the failed device are reconstructed and placed in the spares of the first array, and the block addresses are appropriately remapped to the spares. Distributed spare sharing is possible because the first array is configured to include at least one spare region/row, and the second array will never lose a number of blocks greater than the common number of rows in the first array in a single device failure.

Abstract: In a log structured array (LSA) storage subsystem, a method for recovering from a storage device failure which incorporates the LSA write and garbage collection procedures, thereby simplifying the recovery process and eliminating the need for dedicated or distributed sparing schemes. Data is distributed across the array in N+P parity groups. Upon a device failure, each lost data block is reconstructed from the remaining blocks of its parity group. The reconstructed block is then placed in the subsystem write buffer to be processed with incoming write data, and new parity is generated for the remaining N-1 data blocks of the group. A lost parity block is replaced by first moving one of the data blocks of its parity group to the write buffer, and then generating new parity for the remaining N-1 data blocks. Also disclosed is a storage subsystem implementing the preceding recovery method.