Network Appliance, Inc.

Netapp, Inc.

Tomislav Grcanac

Atul Goel

Jagadish Vasudeva

Sunitha Sunil Sankar

Jeffrey S Kimmel

Rajesh Sundaram

Stephen H Strange

Gururaj Mj

A data access request is received specifying a data block stored in a stripe of a parity group that includes a plurality of data storage devices to store data blocks and a parity storage device to store parity information for the data. The stripe includes a data block from each of the plurality of data storage devices and the stripe includes a parity block from the parity storage device. An error is detected in the data block specified by the data access request. The error is identified as a lost write error for the data block or a lost write error for the parity block. Identifying the error includes comparing a first storage device signature stored in a metadata field associated with the data block to a second storage device signature stored in a label block identifying a data storage device where the data block is stored.

Identifying lost write errors in a raid array

A storage server stores data in a stripe of a parity group that includes a plurality of data storage devices to store data and a parity storage device to store parity information. The stripe includes a data block from each of the data storage devices and a parity block from the parity storage device. The storage server receives a data access request specifying a data block in the stripe, and a lost write detection module detects an error in the data block. The lost write detection module compares a first storage device signature stored in a metadata field associated with the data block to a second storage device signature stored in a global field of the data storage device containing the data block. If the first storage device signature matches the second storage device signature, the lost write detection module compares a consistency point count stored in the metadata field to a reconstructed consistency point count. If the reconstructed consistency point count is greater than the consistency point count stored in the metadata field, the lost write detection module identifies the error as a lost write error for the data block. Accurately detecting and identifying the location of a lost write allows the storage server to correct the error and provide a user with a complete and accurate set of data.

A method and system for recovering data from a 'sick' disk are described. One embodiment of the invention relates to a RAID-based storage system that predicts the failure of a disk (e.g., a 'sick' disk) in a RAID disk group. Accordingly, the storage system allocates a target disk, selected from several spare disks, to replace the &#x201c;sick&#x201d; disk in the RAID disk group upon completion of a disk-to-disk copy operation. Once a target disk has been allocated, a disk-to-disk copy operation is initiated to copy data from the &#x201c;sick&#x201d; disk to the target disk, thereby preventing the need to reconstruct data on the &#x201c;sick&#x201d; disk if the &#x201c;sick&#x201d; disk actually fails. During the disk-to-disk copy operation, client-initiated disk access operations continue to be serviced. Upon completion of the disk-to-disk copy operation, the storage system reconfigures the RAID disk group by swapping the target disk with the &#x201c;sick&#x201d; disk.

Method and system for rapidly recovering data from a 'sick' disk in a RAID disk group

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&#x2212;1 mass storage devices in the redundancy group can be specifically identified as containing the erroneous data.

Lost writes detection in a redundancy group based on RAID with multiple parity

A storage system includes a set of mass storage media and a plurality of functional layers that provide a data storage path between a file system and the set of mass storage media. The storage system can detect that a write issued by the file system was lost by one of the functional layers that provide the data storage path between the file system and the mass storage media.

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San Jose, CA, United States of America

Tomislav Grcanac