Veritas Volume Manager – Adding DRL Log

8. Adding a DRL Log

Dirty region logging (DRL) is used with mirrored volume layouts. DRL keeps track of the regions that have changed due to I/O writes to a mirrored volume. Prior to every write, a bitmap is written to a log to record the area of the disk that is being changed. In case of system failure, DRL uses this information to recover only the portions of the volume that need to be recovered.

To put Dirty Region Logging into effect for a volume, a log subdisk must be added to that volume and the volume must be mirrored. Only one log subdisk can exist per plex.

The following example creates a log for the mirrored volume vol03:

· #vxassist addlog vol03

When vxassist is used to add a log subdisk to a volume, a log plex is also created to contain the log subdisk, by default.

Once created, the plex containing a log subdisk can be treated as a regular plex. Data subdisks can be added to the log plex. The log plex and log subdisk can be removed using the same procedures used to remove ordinary plexes and subdisks.


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