The XP Disk Array uses spare disk drives to take the place of any disk drives that are blocked because of errors or whose error count exceeds a specified limit value. Data from the failed or blocked drive is copied directly to the new spare drive from the failing drive or regenerated from the remaining good drives in the parity group. Because this regeneration or copying is done in the background, the array can continue to accept and respond to host I/O requests while the copying progresses. The data saved on spare disk drives is copied back into the original location after the drive with errors has been replaced with a new one.