Abstract: Embodiments of the present invention provide novel, reliable and efficient technique for tracking, tolerating and correcting unrecoverable errors (i.e., errors that cannot be recovered by the existing RAID protection schemes) in a RAID array by reducing the need to perform drastic recovery actions, such as a file system consistency check, which typically disrupts client access to the storage system. Advantageously, ability to tolerate and correct errors in the RAID array beyond the fault tolerance level of the underlying RAID technique increases resiliency and availability of the storage system.

Abstract: A storage server stores data in a redundancy group of mass storage devices according to a data redundancy scheme. The redundancy scheme enables reconstruction of all data stored in the redundancy group if N or fewer mass storage devices in the redundancy group contain erroneous data, where N is at least 2. In response to determining that the redundancy group contains erroneous data, N?1 mass storage devices in the redundancy group can be specifically identified as containing the erroneous data.

Abstract: A storage system, such as a file server, receives a request to perform a write operation that affects a data block. In response, the storage system writes to a storage device the data block together with context information which uniquely identifies the write operation with respect to the data block. When the data block is subsequently read from the storage device together with the context information, the context information that was read with the data block is used to determine whether a previous write of the data block was lost.

Abstract: A query-based spares management technique enables a storage operating system of a storage system to select disks to be added to one or more RAID groups of a volume. The spares management technique includes an attributes-based disk selection procedure that is performed by the storage operating system in response to an operator-initiated request to add disks to the volume or in response to a demand-driven request resulting from a requirement imposed by the system to add disks to the volume. The disks that are added to the RAID groups of the volume are retrieved from one or more spare pools of disks maintained by the storage system.