Hardware RAID, I forget the raid number but it's a dual IDE, with Pri Master and Sec Master striped, and Pri Slave and Sec Slave striped, and then the stripe sets mirrored.
The problem is that if a minor glitch happens, the RAID card has a fit at bootup, and says it's incorrectly configured, or an invalid RAID set, at which point you have to break the mirror and try and get back in with the intact half of the mirror, which is fraught with difficulties such as, er, it not working, which is where I'm at just now.
Ordinarily, without the "benefits" of the RAID system, the same glitch would give you some sort of error message from the OS, you'd reboot, run chkdsk, and all would be well. You might lose a file. As it is, I'm having to use the excellent File Scavenger which has so far offered a list of just over 150,000 files on the disc, for me to choose which ones I would like it to attempt to think about possibly trying to consider recovering.
I was planning to ditch the RAID anyway, it's just been forced on me a bit earlier than planned. The solution is to make regular backups and not worry about disc failure; so far the failures have been purely from the crapness of the RAID system, so it's kind of self-defeating.