share virtual disks between guests

Is it possible to share virtual disk between two  guests ?

I'd like to  check if this  scenario  may be impelemted  :

• run two rh5 guests
• each guest has  one system disk
• add second  virtual disk on one of these guests
• defince some database on this extra  disk
• in a case of the db failure unmount/detach this  virtual disk from original  guest and  mount/attach it on the second guest  using API .

/Vlad .