Patent ID: 7565575

Claim:
A method of repairing a disk group comprising a plurality of disks, the method comprising: determining a threshold value for a repair time of the disk group, wherein the threshold value represents a duration during which a hard disk failure should be assumed to be transient; maintaining a set of metadata for each hard disk in the disk group, wherein each hard disk stores a set of data blocks, each data block comprising a set of data stored on the hard disk, and wherein the set of metadata for a hard disk comprises information about whether each of the data blocks on the hard disk is current; identifying with a computer a first hard disk in the disk group that has become unavailable, wherein the first hard disk comprises a first set of data blocks; marking as stale, in the set of metadata for the first hard disk, each data block on the first hard disk to which a write attempt is made while the offline disk is unavailable; and repairing the disk group, wherein repairing the disk group comprises: (i) re-creating each of the data blocks marked as stale in the metadata for the first hard disk, if the first hard disk becomes available before the duration specified by the threshold value has expired; and (ii) re-creating the first set of data blocks on one or more additional hard disks in the disk group, if the first hard disk does not become available before the duration specified by the threshold value has expired.