VERITAS Volume Manager 3.5 User's Guide - VERITAS Enterprise Administrator (September 2004)

Volume Tasks
Adding a Log to a Volume
Chapter 4130
Adding a Log to a Volume
The volume Add Log procedure adds the appropriate type of log to a
mirrored or RAID-5 volume.
When used to add a Dirty Region Logging (DRL) log to a mirrored
volume, DRL uses this log to track the regions of the volume that change
due to I/O writes. If a system failure occurs, DRL uses the information in
the log to recover only the portions of the volume that need recovery. This
speeds up recovery time for mirrored volumes.
For DRL to be in effect, a mirrored volume must have at least one DRL
log. You can create additional DRL logs (on different disks) to mirror the
DRL information.
When used to add a log to a RAID-5 volume, the log speeds up the
resynchronization time for RAID-5 volumes after a system failure. A
RAID-5 log maintains a copy of the data and parity being written to the
volume at any given time. If a system failure occurs, VxVM can “replay”
the RAID-5 log to resynchronize the volume. This copies the data and
parity that was being written at the time of failure from the log to the
appropriate areas of the RAID-5 volume. You can create multiple RAID-5
logs (on different disks) to mirror the log information. Ideally, each
RAID-5 volume has at least two logs.
Step 1. Select the mirrored volume or RAID-5 volume to contain the log.
Step 2. Select Actions > Log > Add.
Step 3. By default the “Auto assign destination disks” option will be selected. To
manually assign the destination disks, select the “Manually assign
destination disks” option.
Available disks will appear in the left window. To add destination disks,
select them in the left window and click the Add button. To add all of the
available disks, click the Add All button.
To remove destination disks, select them in the right window and then
click the Remove button. To remove all of the destination disks, click the
Remove All button.
Step 4. Click Apply to create the Log then OK.