Patent ID: 7552357

Claim:
A method comprising: storing data in a redundancy group of mass storage devices according to a data redundancy scheme, wherein the data redundancy scheme enables reconstruction of all data stored in X or fewer mass storage devices in the redundancy group which contain erroneous data, where X is at least 2; and in response to determining that the redundancy group contains erroneous data, specifically identifying X−1 mass storage devices in the redundancy group which contain the erroneous data by reconstructing data on a selected subset of the redundancy group, the selected subset including at least two but fewer than all of the mass storage devices in the redundancy group, comparing the reconstructed data to the stored data in the mass storage devices of the selected subset, if the reconstructed data does not match the stored data for only one of the mass storage devices in the subset, then determining that said one mass storage device contains the erroneous data, and if the reconstructed data does not match the stored data for all of the mass storage devices in the subset, then repeating said reconstructing and said comparing with a different selected subset of the redundancy group.