IBM RS/6000 - Manual (Page 75)

If the disk is part of the root volume group and the filesystems which are on the
disk can't be unmounted, then you can either wait for a reboot of the system or
remove the disk from the volume group, and then re-add the disk by performing the
following:
1. Remove all the mirrored copies from the mirrored disk (for example, if we had a
logical volume called lv00, there were a total of two copies of the logical
volume and the disk which was removed was hdiskx):
rmlvcopy lv 1 hdiskx
2. Reduce the rootvg to remove the disk:
reducevg rootvg hdiskx
3. Remove the device from the ODM:
rmdev -d -l hdiskx
4. Insert the new drive.
5. Configure it to the system:
cfgmgr
6. Extend the root volume group to this disk:
extendvg rootvg hdiskx
7. Recreate the mirrors on the disk, for example:
mklvcopy lv 2 hdiskx
Chapter 3. Hot-Swap Subsystem 51