Patent ID: 7461101

Claim:
A method for reducing data loss in a system having a storage hierarchy, comprising: receiving a read request for read data; recognizing a data failure in a storage device in response to the read request; determining if RAID protection can handle the data failure; searching for a cached source of the read data in response to recognizing the data failure if said RAID protection can not handle the data failure; writing the read data in cache back to the storage device in which a data failure occurred if the read data was found in cache; determining if the read data containing the error has been allocated for storing; writing a blank data block back to the device in which a data failure occurred if the read data containing the error has not been allocated; retrieving the read data from a backup system if the cached source of the data is unavailable; determining if the read data has been updated since the last backup; determining read data updates pertaining to the read data; and rebuilding the read data utilizing a combination of the retrieved data updates and the data from the alternate source.