Raid-0 on external harddisk. How. Help!!!

Hi all,

I am currently working on a macbook pro am want to use an external harddisk for Aperture etc. Since the internal drive of the macbook pro in only 100GB I will do a lot of the stuff via the external drive. This however means that if it crashes all my data will be lost since I don't have a back-up.

My questions are the following:

• I already have a 500 GB (2x250) Lacie Big Disk Extreme (firewire 400/800) which by itself is configured as Raid-0 (ultimate speed). If I buy a second identical Lacie can I then configure both of them together as Raid-1 so I automatically have a back-up? This means that I will have 2x500 GB drives that mirrors each disk for automatic duplication of data. Would this be possible with the "disk utility" option in OSX or in any other way?

• In case it is possible is it mandatory to have identical disks? (not e.g. a 500 GB and a 600GB drive).

Thanks for your help.

Kim