Patent ID: 7143249

Claim:
A method of rebuilding data in a storage device, the method comprising: replacing a failed storage device in a first group of storage devices, the first group of storage devices belonging to a first set of storage devices; writing up-to-date data to the first group of storage devices; determining a difference between data stored in the first set of storage devices and data stored in a second set of storage devices, by comparing a first storage usage information created prior to failure of the failed storage device and a second storage usage information created after the up-to-date data is written to the first group of storage devices, wherein the first storage usage information is a point-in-time representation of a file system and the second storage usage information is another point-in-time representation of the file system; and resynchronizing the first set of storage devices with the second set of storage devices based on the difference, wherein the difference between the first storage usage information and the second storage usage information represents data written to the second set of storage devices when the first set of storage devices is in a degraded state.