Topics: AIX, LVM, System Admin

Mirrorvg without locking the volume group

When you run the mirrorvg command, you will (by default) lock the volume group it is run against. This way, you have no way of knowing what the status is of the sync process that occurs after mirrorvg has run the mklvcopy commands for all the logical volumes in the volume group. Especially with very large volume groups, this can be a problem.

The solution however is easy: Make sure to run the mirrorvg command with the -s option, to prevent it to run the sync. Then, when mirrorvg has completed, run the syncvg yourself with the -P option.

For example, if you wish to mirror the rootvg from hdisk0 to hdisk1:

# mirrorvg -s rootvg hdisk1
Of course, make sure the new disk is included in the boot list for the rootvg:
# bootlist -m normal hdisk0 hdisk1
Now rootvg is mirrored, but not yet synced. Run "lsvg -l rootvg", and you'll see this. So run the syncvg command yourself. With the -P option you can specify the number of threads that should be started to perform the sync process. Usually, you can specify at least 2 to 3 times the number of cores in the system. Using the -P option has an extra feature: there will be no lock on the volume group, allowing you to run "lsvg rootvg" within another window, to check the status of the sync process.
# syncvg -P 4 -v rootvg
And in another window:
# lsvg rootvg | grep STALE | xargs

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