[linux-lvm] Adding a mirror after-the-fact

[Jason Tackaberry]

I know this isn't strictly an LVM question, but ...

Suppose I have a volume group with 1 physical volume, say a 9GB disk.
Now, after some time, I decide I want to mirror this VG with another 9GB
disk.  What options do I have?  AFAICS, the only way to do this would be
to start from scratch?  This is a pretty simple and presumably common
thing to want to do, so I hope I'm wrong.  :)

Cheers,
Jason.