This question pertains to either Linux 2.6 and/or the latest Mac OS/X.
My goal is data integrity, not speed. I have way too much disk space anyway.
I gather under Linux I need to use the mdadm command. Is that right?
First RAID0 is just striping; there's no redundancy or "integrity"
If you want, you can create a RAID1 array across two partitions. However, again if the drive fails it's taking both partitions with it, and you're back to no redundancy.
I'm guessing that you meant to ask about RAID1, since that is mirroring and RAID0 offers NO data protection. You could do this, but this will probably increase the chances of data loss, since the primary thing RAID1 protects you from is drive failure, and you'll be increasing the load on the drive by doubling the writes to it, so it will be more likely to fail.