Time and space efficient technique for creating virtual volume copies
First Claim
1. A non-transitory computer readable medium for a data storage device encoded with a snapshot tree structure and code for managing the snapshot tree structure to provide point-in-time backups of a base volume, wherein:
- the snapshot tree structure comprises;
a first branch, comprising;
the base volume storing a current user data;
a first read-only snapshot descending from the base volume, the first read-only snapshot being created at a first time, the first read-only snapshot storing a first data of the base volume at the first time before the first data is modified in the base volume; and
a second read-only snapshot descending from the first read-only snapshot, the second read-only snapshot being created at a second time earlier than the first time, the second read-only snapshot storing a second data of the base volume at the second time before the second data is modified in the base volume; and
the code comprises instructions to retrieve data from the snapshot tree structure and transmitting the retrieved data to a host device.
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Abstract
A snapshot tree structure includes a base volume storing a current user data at a current time, a first read-only snapshot descending from the base volume, and a second read-only snapshot descending from the first read-only snapshot. The first read-only snapshot is created at a first time earlier than the current time. The first read-only snapshot stores a first data of the base volume at the first time before the first data is modified in the base volume. The second read-only snapshot is created at a second time earlier than the first time. The second read-only snapshot stores a second data of the base volume at the second time before the second data is modified in the base volume.
55 Citations
14 Claims
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1. A non-transitory computer readable medium for a data storage device encoded with a snapshot tree structure and code for managing the snapshot tree structure to provide point-in-time backups of a base volume, wherein:
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the snapshot tree structure comprises; a first branch, comprising; the base volume storing a current user data; a first read-only snapshot descending from the base volume, the first read-only snapshot being created at a first time, the first read-only snapshot storing a first data of the base volume at the first time before the first data is modified in the base volume; and a second read-only snapshot descending from the first read-only snapshot, the second read-only snapshot being created at a second time earlier than the first time, the second read-only snapshot storing a second data of the base volume at the second time before the second data is modified in the base volume; and the code comprises instructions to retrieve data from the snapshot tree structure and transmitting the retrieved data to a host device. - View Dependent Claims (2, 3, 4, 5)
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6. A method for a data storage device to store snapshots that provide point-in-time backups of a base volume using a snapshot tree structure, the method comprising:
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creating a first branch, comprising; creating the base volume storing a current user data; creating a first read-only snapshot descending from the base volume, the first read-only snapshot being created at a first time; storing in the first read-only snapshot a first data of the base volume at the first time before the first data is modified in the base volume; creating a second read-only snapshot descending from the base volume, the second read-only snapshot being created at a second time later than the first time; storing in the second read-only snapshot a second data of the base volume at the second time before the second data is modified in the base volume; and inserting the second read-only snapshot between the base volume and the first read-only snapshot, wherein the first read-only snapshot now descends from the second read-only snapshot; and retrieving data from the snapshot tree structure and transmitting the retrieved data to a host device. - View Dependent Claims (7, 8, 9, 10)
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11. A method for a data storage device to retrieve a point-in-time backup of a base volume by reading a value of a data block from a snapshot tree structure having the base volume, a first snapshot descending from the base volume, and a second snapshot descending from the first snapshot, the method comprising:
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searching for the data block in the second snapshot; if the data block is not found in the second snapshot; following a link in the second snapshot to the first snapshot; and searching for the data block in the first snapshot; and transmitting the data block to a host device after the data block is found. - View Dependent Claims (12, 13, 14)
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Specification