On 5-16-2000, one machine started getting many errors on its single
hdisk0, rootvg.  This was getting so bad, I had to run fsck on many
different file systems, but it wasn't so bad the system wouldn't run.

  I finally stuck in another 9GB drive and copied over all the data
on hdisk0 to the new hdisk1.  I did this by mirroring all the LV's in
rootvg.  It actually went slicker 'n snot.  Here are the commands in
case I need to do it again.

  mirrorvg rootvg hdisk1     <--- This mirrors all LV's from rootvg
                                  except for your dump LV, if there
                                  is one.
  migratepv -l /dev/dumplv   <--- This, you have to do manually.  And
                                  notice this is a migrate, not a mirror.
  syncvg -v rootvg     <--- This is what actually causes the data to
                            get copied to hdisk1, thus will take a while.
You can now verify for yourself that all LV's are copied over and a
  lsvg -l rootvg
command shows all LV's in "syncd" state, not "stale".

Now you want to rewrite the boot record on hdisk0 in order to tell
it about the new, rootvg mirror, your hdisk1.
  bosboot -ad /dev/hdisk0   <--- Not hdisk1, like I had thought you'd want.

Now change your bootlist to put your new hdisk1, first.
  bootlist -m normal -o hdisk1 hdisk0
  reboot -q

When the system comes back up, you can break all the hdisk0 mirrors and
remove hdisk0 from rootvg.
  unmirrorvg rootvg hdisk0
  reducevg   rootvg hdisk0

And again, rewrite the boot record
  bosboot -ad /dev/hdisk1

An interesting side affect to this procedure is your new disk is "stuck"
at hdisk1.  Even if you rmdev the old hdisk0 and reboot, this new disk
never gets configured as hdisk0.

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  When mirroring disks, to avoid the volume group from going offline
if/when a disk dies, you need to go into smitty and turn off the quorum.

smitty shows this VG attribute as
"A QUORUM of disks required to keep the volume group on-line ?"
and offers you a yes/no choice (the default is yes).

A lsvg command shows this attribute as "QUORUM: 2" for a simple, 2-disk
mirror.

The chvg command to set this off is chvg -Qn afsvg for example, which
changes the lsvg command to show "QUORUM: 1".

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