Unmirror rootvg (Root Volume Group) in AIX

Root Volume Group (rootvg) is a volume group containing the Base Operating System (BOS). Logical volume (lv) in rootvg may be doubled or more in copies with 2 or more physical volume (hard disk) for availability and reliability of the AIX system. The following steps are to unmirror a rootvg, if for whatever reason the rootvg needs to run on single logical volume (lv) on single physical volume (pv) only.

Check and Determine if rootvg is Mirrored

In mirror mode, each logical volume in rootvg such as filesystems “/”, “/usr”, “/var”, “/tmp”, “/home”, “/opt” and default boot, paging and jfslog LVs should be mirrored. In AIX, mirrorvg will create additional copy of image for all logical volumes in the volume group.

Use the following command to check if a rootvg is mirrored:

# lsvg -l rootvg

If the output shows that for each LP there are 2 PPs then its mirrored.

Check and Determine Which Disks the Mirrored rootvg is Located

For each logical volume (LV) name listed in output of “lsvg -l rootvg” command, run the following command:

lslv -m <lv name>

The output date will tell you on which disk each copy of each logical partitions for each LV.

Unmirror rootvg

Important: The following instructions have the risk of making your AIX system unbootable or corrupting the data. So make you have advanced system administration experience before running the process of unmirroring.

To unmirror the root volume group (rootvg), follow the steps below (scenario: rootvg is contained on hdisk01 and mirrored onto hdisk11, and the steps will remove the mirror on hdisk11 (regardless of the disk from which you previously booted)):

1. To unmirror the rootvg from hdisk11, enter the following command:

   unmirrorvg rootvg hdisk11

   This command turns quorum back on for rootvg. When unmirrorvg is executed, the default COPIES value for each logical volume becomes 1.

2. To update the booted disk link, enter the following command:

   ln -f /dev/rhdisk01 /dev/ipldevice

3. To reduce the disk out of rootvg, type the following command:

   reducevg rootvg hdisk11

4. To initilize the boot record of the remaining disk again, enter the following command:

   bosboot -a -d /dev/hdisk01

   bosboot command is a must to initialize the boot record on the remaining disk hdisk01 again.

5. To modify the boot list to remove the unmirrored disk, type the following command:

   bootlist -m normal hdisk01

   bootlist command is a must so that the system only boots to the disk remaining (hdisk01) in rootvg.

6. Restart AIX machine, as unmirroring turns quorum back on for rootvg, a reboot is required for this to take effect.

Note: The reducevg command in step 3 will fail if there are non-mirrored logical volumes such as raw logical volumes and system dump devices on the disk.