Patent ID: 8082390

Claim:
A method for obtaining RAID group consistency information for a slice of data included on a device comprising: receiving a request for data stored in the slice; mapping the slice to an index, the index being one of a plurality of indices each associated with a structure indicating RAID group inconsistencies for a different portion of slices of data of the device; if the index is not associated with a structure, determining that there is no RAID group inconsistency for the slice; if the index is associated with a structure, performing: determining a hint bit associated with the slice, wherein the hint bit encodes summary consistency information for data and parity information for a plurality of slices, each of the plurality of slices including information stored on a plurality of different member devices of a RAID group, said hint bit being set if there is a RAID group inconsistency for information of any of the plurality of slices stored on any of the plurality of the different member devices; determining whether the hint bit is set; and if the hint bit is not set, determining that there is no RAID group inconsistency for any of the plurality of slices including the slice and servicing the request without performing a rebuild operation on a RAID group member device that stores the slice containing the data responsive to the request, and if the hint bit is set, performing processing to obtain additional slice-level RAID group consistency information of the structure for the slice to make a further determination as to whether the request is able to be serviced without performing a rebuild operation on a RAID group member device for the slice using at least some of the data and parity information.