That should work with Linux software RAID yeah. You may want to drop the mirror and just create RAID0's, using one for backup. That would still be quite safe, protected from most dangers. You still rely on the same RAID layer for access to your data though.
By the way, don't you want to try out ZFS? If you don't know yet, you should read up (on wikipedia) on what ZFS is and why it's so great.