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Copy-on-write

In Updates to the primary fileset, the third block originally containing C is updated. Before the block is updated with new data, the original data is copied to the Storage Checkpoint. This is called the copy-on-write technique, which allows the Storage Checkpoint to preserve the image of the primary fileset when the Storage Checkpoint is taken.

Every update or write operation does not necessarily result in the process of copying data to the Storage Checkpoint. In this example, subsequent updates to this block, now containing C', are not copied to the Storage Checkpoint because the original image of the block containing C is already saved.

Updates to the primary fileset

Updates to the primary fileset

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