Patent ID: 8037345

Claim:
A file server comprising: physical data storage; and at least one data processor coupled to the physical data storage for accessing the physical data storage; wherein said at least one data processor is programmed for maintaining a sparse metavolume of the physical data storage, the sparse metavolume includes slices of the physical data storage allocated to the sparse metavolume, the sparse metavolume provides logical data storage, some of the logical data storage is mapped to the slices of the physical data storage allocated to the sparse metavolume, some of the logical data storage does not have allocated physical storage and is not mapped to the slices of the physical data storage allocated to the sparse metavolume, and the sparse metavolume has slice metadata defining the allocation of the slices of the physical data storage to the sparse metavolume and the mapping of the logical data storage to the slices of the physical data storage that are allocated to the sparse metavolume, and wherein the file server stores three copies of the slice metadata, and said at least one data processor is programmed with a recovery program executable by said at least one data processor to recover from a disruption by comparing the three copies of the slice metadata to detect and correct errors in the slice metadata.