On Thu, 30 Mar 2000, Theo Van Dinter wrote:
> On Thu, Mar 30, 2000 at 08:36:52AM -0600, Bill Carlson wrote:
> > I've been thinking about this for a different project, how bad would it be
> > to setup RAID 5 to allow for 2 (or more) failures in an array? Or is this
> > handled under a different class of RAID (ignoring things like RAID 5 over
> > mirrored disks and such).
>
> You just can't do that with RAID5. I seem to remember that there's a RAID 6
> or 7 that handles 2 disk failures (multiple parity devices or something like
> that.)
>
> You can optionally do RAID 5+1 where you mirror partitions and then stripe
> across them ala RAID 0+1. You'd have to lose 4 disks minimally before the
> array goes offline.
1+5 would still fail on 2 drives if those 2 drives where both from the
same RAID 1 set. The wasted space becomes more than N/2, but it might
worth it for the HA aspect. RAID 6 looks cleaner, but that would require
someone to write an implementation, whereas you could do RAID 15 (51?)
now.
My thought here is leading to a distributed file system that is server
independent, it seems something like that would solve a lot of problems
that things like NFS and Coda don't handle. From what I've read GFS is
supposed to do this, never hurts to attack a thing from a couple of
directions.
Use the net block device, RAID 15 and go. Very tempting...:)
Bill Carlson
------------
Systems Programmer [EMAIL PROTECTED] | Opinions are mine,
Virtual Hospital http://www.vh.org/ | not my employer's.
University of Iowa Hospitals and Clinics |
