Splitting a mirrored disk from a volume group
Snapshot support helps you protect the consistency of your mirrored volume groups from potential disk failure.
Using the snapshot feature, you can split off a mirrored disk or disks to use as a reliable (from the standpoint of the LVM metadata) point-in-time backup of a volume group, and, when needed, reliably reintegrate the split disks into the volume group. In the following procedure, you first split off a mirrored disk from a volume group and then you merge the split-off disk into the original volume group. To further ensure the reliability of your snapshot, file systems must be unmounted and applications that use raw logical volumes must be in a known state (a state from which the application can recover if you need to use the backup).
- A disk is already missing.
- The last non-stale partition would be on the split-off volume group.
- Any stale partitions exist in the volume group, unless you use the force flag (-f) with the splitvg command.
Furthermore, the snapshot feature (specifically, the splitvg command) cannot be used in enhanced or classic concurrent mode. The split-off volume group cannot be made concurrent or enhanced concurrent and there are limitations to the changes allowed for both the split-off and the original volume group. For details, read the chvg command description.
The information in this how-to scenario was tested using specific versions of AIX®. The results you obtain might vary significantly depending on your version and level of AIX.
- Ensure that the volume group is fully mirrored and that the mirror exists on a disk or set of disks that contains only this set of mirrors.
- To enable snapshot support, split off the original volume
origVG) to another disk or set of disks, using the following command:
splitvg origVGAt this point, you now have a reliable point-in-time backup of the original volume group. Be aware, however, that you cannot change the allocation on the split-off volume group.
- Reactivate the split-off disk and merge it into the original
volume group using the following command:
joinvg origVGAt this point, the split-off volume group is now reintegrated with the original volume group.