--> Dumb question, but why would you want OS mirroring when you have TSM do
the mirroring between two Raw LV's

Obviously TSM supports only DB & Log volumes mirroring. The mirroring of
the random access volumes should be done by hardware or at OS level.
Unless in some of the next versions LVM is used for the diskpool volumes.

--> If I wanted TSM support I would need to do TSM mirroring.

I would be happy to get this written clearly in the manuals. If there is
no such thing in the docs, the statement is incorrect.

--> You could just format a bunch of 2G storage pool volumes.  You know what
size they are and they format a lot faster.

They will format a lot faster and will run a lot slower. Your disk head(s)
will start thrashing when you need to use those volume under certain load.
I (personally) would prefer to do more work once and have much less
trouble later.

Zlatko Krastev
IT Consultant