Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Storage Checkpoints
How a Storage Checkpoint Works
Chapter 578
the specified data block on the primary fileset do not result in additional updates to the Storage Checkpoint
because the old data needs to be saved only once. As blocks in the primary fileset continue to change, the
Storage Checkpoint accumulates the original data blocks.
In the following figure, 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.
Figure 5-3 Updates to the Primary Fileset