On Wed, 18 Aug 2004, John T. Hoffoss wrote: > Actually, according to this site <http://www.acnc.com/04_01_05.html>, > RAID5 is distributed parity. Perhaps this is vendor-specific though. > Effectively, this leads to "one parity drive". (X drives of size N > results in X parity slices of size N/X, one per drive, which results in > usable storage space equivalent to XN - N .) Er, yeah, thanks for the clarification - parity blocks are spread across all disks, and use the equivilent of one drive's space. What I described (dedicated parity drive) would technically be RAID 3. That's what I get for shooting of a reply while on vacation. :) RAID6 stores two identical blocks of parity, so you lose the usable space of two drives, and can also lose two drives without losing data. Back to Sam's original scenario (losing two RAID5 drives without losing data) - I have also seen cases where drives are failing (not totally dead), and the RAID controller will still be able to access data from te failing drive - in that case, you could appear to lose two drives in RAID5 without losing data. -- Nate Carlson <natecars at real-time.com> | Phone : (952)943-8700 http://www.real-time.com | Fax : (952)943-8500 _______________________________________________ TCLUG Mailing List - Minneapolis/St. Paul, Minnesota Help beta test TCLUG's potential new home: http://plone.mn-linux.org Got pictures for TCLUG? Beta test http://plone.mn-linux.org/gallery tclug-list at mn-linux.org https://mailman.real-time.com/mailman/listinfo/tclug-list