Recovery of file system data in file servers mirrored file system volumes
First Claim
1. A method comprising:
- creating at least one snapshot for each mirrored file system volume of a plurality of file system volumes;
including a consistency point value in said at least one snapshot indicating a sequence in which said at least one snapshot was generated;
examining the plurality of mirrored file system volumes for consistency point values; and
determining a most up-to-date said file system volume based on the consistency point values.
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Abstract
The invention provides a method and system for recovery of file system data in file servers having mirrored file system volumes. The invention makes use of a “snapshot” feature of a robust file system (the “WAFL File System”) disclosed in the Incorporated Disclosures, to rapidly determined which of two or more mirrored volumes is most up-to-date, and which file blocks of the most recent mirrored volume have been changed from each one of the mirrored file systems. In a preferred embodiment, among a plurality of mirrored volumes, the invention rapidly determines which is the most up-to-date by examining a consistency point number maintained by the WAFL File System at each mirrored volume. The invention rapidly pairwise determines what blocks are shared between that most up-to-date mirrored volume and each other mirrored volume, in response to a snapshot of the file system maintained at each mirrored volume and are stored in common pairwise between each mirrored volume and the most up-to-date mirrored volume. The invention re synchronizes only those blocks that have been changed between the common snapshot and the most up-to-date snapshot.
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Citations
19 Claims
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1. A method comprising:
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creating at least one snapshot for each mirrored file system volume of a plurality of file system volumes; including a consistency point value in said at least one snapshot indicating a sequence in which said at least one snapshot was generated; examining the plurality of mirrored file system volumes for consistency point values; and determining a most up-to-date said file system volume based on the consistency point values. - View Dependent Claims (2, 3, 4, 5, 6, 19)
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7. An apparatus comprising:
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a plurality of mirrored file system volumes, each having at least one snapshot including an entire consistent file system, each said snapshot having a consistency point value indicating a sequence in which each said snapshot was generated; a first comparison element capable of being coupled to a plurality of said consistency point values and capable of determining a most up-to-date mirrored file system volume of the plurality of mirrored file system volumes based on the consistency point values; and a second comparison element, responsive to an output of said first comparison element, said second comparison element being capable of being coupled (a) to a first snapshot associated with said most up-to-date mirrored file system volume and (b) to a second snapshot associated with a second said volume, said second comparison element being capable of providing a selection of file blocks that differ between said second volume and said most up-to-date mirrored file system volume. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus to maintain a plurality of mirrored file system volumes, the apparatus comprising:
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a first element capable of creating at least one snapshot for each mirrored file system volume of the plurality of mirrored file system volumes and including a consistency point value in said at least one snapshot indicating a sequence in which said at least one snapshot was generated; a second element capable of examining the snapshots of the plurality of mirrored file system volumes for consistency point values; and a third element capable of determining a most up-to-date said file system volume based on the consistency point values.
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Specification