RAID-1 / -5 is mainly good for "real time" backup, not for long-term data safety. So no, I use CD-Rs (DVD-Rs soon) and offsite backup for data safety.
RAID won't protect you from:
- virus / worm / rogue OS / bad MS "patch"
- catastrophic power supply failure
- IDE controller and drive cable problems (data corruption)
- server theft
I did use "manual RAID 1" to back up my 800 FLAC'd CDs though, i.e. I copied all files on 1 - 250 GB drive to another. But then I removed the backup drive from the box to protect me from the failure points above.