CLUSTERED FILESYSTEM WITH DATA VOLUME SNAPSHOT MAINTENANCE
First Claim
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1. A method of maintaining a copy of at least one data volume in a computer system for at least one point in time, comprising:
- initiating creation of a first snapshot of a base volume;
establishing a first repository for the first snapshot of the base volume;
creating a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed;
monitoring the base volume for write operations thereto;
identifying a write operation to a first region of the base volume;
determining whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and
prior to a write operation to the first region of the base volume, copying the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot.
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Abstract
A computer system with read/write access to storage devices creates a snapshot of a data volume at a point in time while continuing to accept access requests to the mirrored data volume by copying before making changes to the base data volume. Multiple snapshots may be made of the same data volume at different points in time. Only data that is not stored in a previous snapshot volume or in the base data volume are stored in the most recent snapshot volume.
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Citations
20 Claims
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1. A method of maintaining a copy of at least one data volume in a computer system for at least one point in time, comprising:
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initiating creation of a first snapshot of a base volume; establishing a first repository for the first snapshot of the base volume; creating a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed; monitoring the base volume for write operations thereto; identifying a write operation to a first region of the base volume; determining whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and prior to a write operation to the first region of the base volume, copying the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot. - View Dependent Claims (2, 3, 4, 5, 6, 7, 14)
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8. A system for maintaining a copy of at least one data volume in a computer system for at least one point in time, comprising:
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means for initiating creation of a first snapshot of a base volume; means for establishing a first repository for the first snapshot of the base volume; means for creating a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed; means for monitoring the base volume for write operations thereto; means for identifying a write operation to a first region of the base volume; means for determining whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and prior to a write operation to a first region of the base volume, means for copying the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot. - View Dependent Claims (9, 10, 11, 12, 13)
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15. A computer readable storage medium including code for maintaining a copy of at least one data volume in a computer system for at least one point in time, the code when executed operable to:
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initiate creation of a first snapshot of a base volume; establish a first repository for the first snapshot of the base volume; create a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed; monitor the base volume for write operations thereto; identify a write operation to a first region of the base volume; determine whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and prior to a write operation to the first region of the base volume, copy the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification