Take a look at the Software RAID howto for lots of useful information.
http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html
But basically Raid-0 is no better, reliability wise, than a single harddrive. It just provides better performance because it is writing to multiple drives.
Level 1 mirrors between the drives so that when one finally fails the data is still on the other drive(s).
bcl