One thing you may want to consider - booting off /dev/sd0a, and mounting the rest as raid, and mirroring /dev/sd0a to /dev/sd1a so that you can swap a cable and be on the alternate /dev/sd0a. This should not be a big deal, since the root partition should not change that much, and a nightly rsync should capture everything that changed that day, if any.
One thing about a software raid solution - you may still have to swap cables in order to get it to boot off the second hard drive anyway (no idea about sata, but I've not seen any motherboard that can boot off the slave ata drive).
