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Fault Detection

Method-and-apparatus-for-identifying-and-repairing-mismatched-data

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Method and apparatus for identifying and repairing mismatched data

Details

Inventors: Kedem, Ishay;
Assignee: EMC Corporation (Hopkinton, MA)
Primary Examiner: Wiley; David A.
Assistant Examiner:
Attorney, Agent or Firm: Wolf, Greenfield & Sacks, P.C.

Method and apparatus are disclosed for resolving data coherence problems (or mismatched data caused by a failure to update data) in a storage system that includes redundant information. The data may be stored as CKD records or fixed size blocks. The method and apparatus may identify data coherence problems by comparing fields for which the correct value is known in advance, by comparing fields between more than one copy of corresponding data units and through other disclosed techniques.

DETAILED DESCRIPTION According to one embodiment of the present invention, a method of determining if a data coherence problem exists in a storage system is disclosed.
According to this embodiment, a data unit format value, stored in each copy of a plurality of corresponding copies of a data unit, is compared with a known correct value.
Based on the comparison, copies which do not include correct data are identified.
The data unit may be stored on one of a plurality of mirrors in the storage system and may be a fixed block size.
The method may include the step of repairing data units determined not to be correct.
The data unit format value may vary, depending on the intended physical location of the data unit in the respective mirror.
For example, the data unit format value may include a logical block address.
According to another embodiment of the present invention, a storage system is disclosed.
According to this embodiment, the storage system includes a plurality of storage devices, storing a redundancy group.
The storage system includes a data coherence tester, that comprises means for comparing a data unit format value, stored in each corresponding copy of a data unit, with a correct value known in advance.
The storage system may include means for determining which of the copies do not have correct data.
According to another embodiment of the present invention, a method of determining if a data coherence problem exists in a storage system is disclosed.
According to this embodiment, a plurality of corresponding copies of a data unit are provided.
The method determines whether a data coherence problem exists among the copies, but without an exhaustive examination of the actual user data in the data unit.
The step of determining whether a data coherence problem exists may comprise a step of comparing error code information stored in corresponding copies of the data unit.
The data unit itself may be stored on one of a plurality of mirrors in the storage system.
According to another embodiment of the present invention, a storage system is disclosed

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