VERITAS File System 4.1 Administrator's Guide

Storage Checkpoints
How a Storage Checkpoint Works
Chapter 594
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