| 摘要 |
<p>A RAID system includes an array of disk units, with data mapped on to the disks as a series of stripes. Each stripe contains a number of chunks, including at least one data chunk and at least one parity chunk. The data chunks of each stripe are located on radially more outer parts of the disks and the parity chunks of each stripe are located on radially more inner parts of the disks. Because the data chunks are all located on the radially more outer parts of the disks, the amount of head movement for read operations is significantly reduced, which significantly improves the read performance. If each stripe contains d data chunks and p parity chunks, the data chunks are located on the radially more outer fraction d/(d+p) of each disk, and the parity chunks are located on the radially more inner fraction p/(d+p) of each disk. Successive chunks within each stripe may be physically located at successively more radially inward positions on successive disks, so that each stripe has a helical configuration. Mirroring can be considered as a special case in which the number of data chunks is equal to the number of parity chunks, and the parity consists of a simple replication of the data. A mirrored data storage disk array is described in which data is written to the outermost half of one disk, and to the innermost half of another disk, and is read from the disk in which it is stored in the outermost half. <IMAGE></p> |
