?????? RAID1 can only handle 1 failure also!! If you are a decent administrator, you'll act when a disk becomes flaky, or as soon as it fails. (Of course, if 2 disks go at the same time, you're hosed, but that's the case for RAID1 also...)
Hmmm, probably I wasn't very clear.What I mean here is that if you stuff an array of 10 RAID 5 disks the chance that two disks will fail at the same time will be quite high. Much higher than with two mirrored disks. So, statistically, a small array is safer than a big one.
Moreover if two disks in an array of ten fail, you will lose the content of nine disks. If a mirrored pair fail you lose just one disk.
I would say that the use of a spare disk is recommended in any case. ;) Massimiliano -- Massimiliano Ferrero Midhgard s.r.l. C/so Re Umberto 23 10128 - Torino tel. +39-0112301400 - fax +39-0112301422 e-mail: m.ferrero@midhgard.it sito web: http://www.midhgard.it