[linux-lvm] 2 LVM questions

[moka at hol.gr]

Hi there, new to LVM, so I would appreciate if you can 
point me to answers to these questions:

1) I have a system with 3 hard disks, and only one of 
them is presently used. This contains boot, root and 
swap plus a logical  partition(not LVM) containing
/var and /home.

I have big database tables, so I would like
 to create one volume group consisting of the 2
 unused disks plus the /var. Is this possible
 without losing what is in /var?
2) The reason I need  a lot of space is that mysql
  which I am using stores the database tables in /var.
 Can I somehow "name" the volume group /var
  so that mysql will not be confused?

Thanks in advance,
S.Alexiou