You will have to reinstall because if you add two more 500GB drives to make your set up into a three drive horse, you then need to format each drive and synchronise them together creating the new logical RAID volume so no data can be kept on said disks prior to the creation of the RAID.

HTH!

--
Regards,
James ;)

Joan Crawford  - "I, Joan Crawford, I believe in the dollar. Everything I earn, I spend."