Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

Note: Synchronization of a full-sized instant snapshot from the original volume
is enabled by default. If you specify the syncing=no attribute to vxsnap make, this
disables synchronization, and the contents of the instant snapshot are unlikely
ever to become fully synchronized with the contents of the original volume at the
point in time that the snapshot was taken. In such a case, the snapshot cannot be
used for off-host processing, nor can it become an independent volume.
You can immediately retake a full-sized or space-optimized instant snapshot at
any time by using the vxsnap refresh command. If a fully synchronized instant
snapshot is required, the new resynchronization must first complete.
To create instant snapshots of volume sets, use volume set names in place of
volume names in the vxsnap command.
See “Creating instant snapshots of volume sets” on page 381.
When using the vxsnap prepare or vxassist make commands to make a volume
ready for instant snapshot operations, if the specified region size exceeds half
the value of the tunable voliomem_maxpool_sz , the operation succeeds but gives
a warning such as the following (for a system where voliomem_maxpool_sz is set
to 12MB):
VxVM vxassist WARNING V-5-1-0 Specified regionsize is
larger than the limit on the system
(voliomem_maxpool_sz/2=6144k).
See “DMP tunable parameters ” on page 540.
If this message is displayed, vxsnap make, refresh and restore operations on
such volumes fail as they might potentially hang the system. Such volumes can
be used only for break-off snapshot operations using the reattach and make
operations.
To make the volumes usable for instant snapshot operations, use vxsnap
unprepare on the volume, and then use vxsnap prepare to re-prepare the volume
with a region size that is less than half the size of voliomem_maxpool_sz (in this
example, 1MB):
# vxsnap -g mydg -f unprepare vol1
# vxsnap -g mydg prepare vol1 regionsize=1M
See “Preparing to create instant and break-off snapshots” on page 367.
See “Creating and managing space-optimized instant snapshots” on page 371.
See “Creating and managing full-sized instant snapshots” on page 373.
See “Creating and managing third-mirror break-off snapshots” on page 375.
365Administering volume snapshots
Creating instant snapshots