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 respective bit representing each region of the base volume, each bit indicating whether any data in a respective 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;
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; and
upon reinitialization of a system maintaining the first repository, rebuilding the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the system.
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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.
161 Citations
18 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 respective bit representing each region of the base volume, each bit indicating whether any data in a respective 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; 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; and upon reinitialization of a system maintaining the first repository, rebuilding the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the system. - View Dependent Claims (2, 3, 4, 5, 6)
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7. 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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one or more processors; and memory storing instructions, the instructions, when executed by the one or more processors, cause the processors to perform operations 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 respective bit representing each region of the base volume, each bit indicating whether any data in a respective 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; prior to a write operation to a 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; and upon reinitialization of a system maintaining the first repository, rebuilding the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the system. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A non-transitory 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 respective bit representing each region of the base volume, each bit indicating whether any data in a respective 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; 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; and upon reinitialization of a system maintaining the first repository, rebuild the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the system. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification