I just wanted to set up a RAID1, to have something I can count on. But then I started to think about it: What happens, if you have a power failure (hard switch off) in a system with e.g. reiserfs and RAID1? On the one HD, the writing transaction may got finished until poweroff, and on the 2nd HD the write transaction was still ongoing. So at the next poweron, the write gets rolled back on the 2nd HD, but not on the 1st HD. Now you have a mirrored system with not identical data.

Do you have any idea, how (or if) this is solved?