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

Chapter 9, Administering Volume Snapshots
Creating a Volume for Use as a Full-Sized Instant Snapshot
293
volume. The default size of 1m (1MB) is suggested as the minimum
value for high-performance array and controller hardware. The
specified value is rounded to a multiple of the volume’s region size.
slow=iodelay Specifies the delay in milliseconds between synchronizing
successive sets of regions as specified by the value of iosize. This
can be used to change the impact of synchronization on system
performance. The default value of iodelay is 0 milliseconds (no
delay). Increasing this value slows down synchronization, and
reduces the competition for I/O bandwidth with other processes
that may be accessing the volume.
Options may be combined as shown in the following examples:
# vxsnap -g mydg -o iosize=2m,slow=100 make \
source=myvol/snapvol=snap2myvol/syncing=on
# vxsnap -g mydg -o iosize=10m,slow=250 syncstart snap2myvol
Note These optional parameters only affect the synchronization of full-sized instant
snapshots. They are not supported for space-optimized snapshots.
Creating a Volume for Use as a Full-Sized Instant Snapshot
If you want to create a full-sized instant snapshot for an original volume that does not
contain any spare plexes, you can use an empty volume with the required degree of
redundancy, and with the same size and same region size as the original volume.
To create an empty volume for use by a full-sized instant snapshot:
1. Use the vxprint command on the original volume to find the required size for the
snapshot volume.
# LEN=‘vxprint [-g diskgroup] -F%len volume‘
Note The command shown in this and subsequent steps assumes that you are using a
Bourne-type shell such as sh, ksh or bash. You may need to modify the
command for other shells such as csh or tcsh.
2. Use the vxprint command on the original volume to discover the name of its DCO:
# DCONAME=‘vxprint [-g diskgroup] -F%dco_name volume‘
3. Use the vxprint command on the DCO to discover its region size (in blocks):
# RSZ=‘vxprint [-g diskgroup] -F%regionsz $DCONAME‘