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

Chapter 9, Administering Volume Snapshots
Traditional Third-Mirror Break-Off Snapshots
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Traditional Third-Mirror Break-Off Snapshots
The traditional third-mirror break-off volume snapshot model that is supported by the
vxassist command is shown in “Third-Mirror Snapshot Creation and Usage.” This
figure also shows the transitions that are supported by the snapback and snapclear
commands to vxassist.
Third-Mirror Snapshot Creation and Usage
The vxassist snapstart command creates a mirror to be used for the snapshot, and
attaches it to the volume as a snapshot mirror. (The vxassist snapabort command can
be used to cancel this operation and remove the snapshot mirror.)
Note As is usual when creating a mirror, the process of copying the volume’s contents to
the new snapshot plexes can take some time to complete. For methods of making
snapshot plexes immediately available, see “Full-Sized Instant Snapshots” on
page 265 and “Space-Optimized Instant Snapshots” on page 267.
When the attachment is complete, the vxassist snapshot command is used to create a
new snapshot volume by taking one or more snapshot mirrors to use as its data plexes.
The snapshot volume contains a copy of the original volume’s data at the time that you
took the snapshot. If more than one snapshot mirror is used, the snapshot volume is itself
mirrored.
Original
volume
Refresh on
snapback
vxassist snapstart
vxassist snapback
vxassist snapclear
Original
volume
Independent
volume
Back up to disk,
tape or other
media, or use to
create replica
database or file
system.
Backup
Cycle
START
vxassist snapshot
Snapshot
volume
Snapshot
mirror