Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

274 Administering volumes

Adding a RAID-5 log

Note: You need a full license to use this feature.

Only one RAID-5 plex can exist per RAID-5 volume. Any additional plexes become

RAID-5 log plexes, which are used to log information about data and parity being written

to the volume. When a RAID-5 volume is created using the

vxassist command, a log

plex is created for that volume by default.

To add a RAID-5 log to an existing volume, use the following command:

# vxassist [-b] [-g diskgroup] addlog volume [loglen=length]

Note: If specified, the -b option makes adding the new log a background task.

You can specify the log length used when adding the first log to a volume. Any logs that

you add subsequently are configured with the same length as the existing log.

For example, to create a log for the RAID-5 volume volraid, in the disk group, mydg,

use the following command:

# vxassist -g mydg addlog volraid

Adding a RAID-5 log using vxplex

As an alternative to using vxassist, you can add a RAID-5 log using the vxplex

command. For example, to attach a RAID-5 log plex, r5log, to a RAID-5 volume,

r5vol, in the disk group, mydg, use the following command:

# vxplex -g mydg att r5vol r5log

The attach operation can only proceed if the size of the new log is large enough to hold all

of the data on the stripe. If the RAID-5 volume already contains logs, the new log length is

the minimum of each individual log length. This is because the new log is a mirror of the

old logs.

If the RAID-5 volume is not enabled, the new log is marked as BADLOG and is enabled

when the volume is started. However, the contents of the log are ignored.

If the RAID-5 volume is enabled and has other enabled RAID-5 logs, the new log’s

contents are synchronized with the other logs.

If the RAID-5 volume currently has no enabled logs, the new log is zeroed before it is

enabled.

Removing a RAID-5 log

To identify the plex of the RAID-5 log, use the following command: