Veritas FlashSnap Point-In-Time Copy Solutions 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

12 Point-in-time copy solutions
Software used in point-in-time copy scenarios
Note: As space-optimized instant snapshots only record information about
changed regions in the original volume, they cannot be moved to a different disk
group. They are therefore unsuitable for the off-host processing applications
that are described in this document.
The contents of full-sized instant snapshots must be fully synchronized with the
unchanged regions in the original volume before such snapshots can be moved
into a different disk group and deported from a host.
For more information, see the Veritas Volume Manager Administrator’s Guide.
Storage Checkpoints
A Storage Checkpoint is a persistent image of a file system at a given instance in
time. Storage Checkpoints use a copy-on-write technique to reduce I/O overhead
by identifying and maintaining only those file system blocks that have changed
since a previous Storage Checkpoint was taken. Storage Checkpoints have the
following important features:
■ Storage Checkpoints persist across system reboots and crashes.
■ A Storage Checkpoint can preserve not only file system metadata and the
directory hierarchy of the file system, but also user data as it existed when
the Storage Checkpoint was taken.
■ After creating a Storage Checkpoint of a mounted file system, you can
continue to create, remove, and update files on the file system without
affecting the image of the Storage Checkpoint.
■ Unlike file system snapshots, Storage Checkpoints are writable.
■ To minimize disk space usage, Storage Checkpoints use free space in the file
system.
Storage Checkpoints and the Storage Rollback feature of Veritas Storage
Foundation for Databases enable rapid recovery of databases from logical errors
such as database corruption, missing files and dropped table spaces. You can
mount successive Storage Checkpoints of a database to locate the error, and
then roll back the database to a Storage Checkpoint before the problem
occurred. For more information, see “Database recovery” on page 57.
For more information about the implementation of Storage Checkpoints, see the
Veritas File System Administrator’s Guide.