[geeks] recommended dual channel LVD controller, PC

[Scott Howard]

On Sat, Jul 24, 2004 at 03:12:05PM -0400, Phil Stracchino wrote:
> > So what about RAID 1+5?
> 
> 1+5 is somewhat of a meaningless combination.  I can think of no
> rational reason for doing it.

You'd be surprised how many people actally mirrored RAID-5 volumes.
Generally it's done as a combination of two hardware RAID-5 arrays
mirrored to each other. It gives a good combination of double
redundancy at the disk level (and having seen double-disk failures
more than one this isn't a bad thing!) as well as full redundancy of
the hardware RAID array itself (plus cables/cards/etc).

You could get similar redundancy with RAID 1+0 between disks in the
two arrays, but then if you lose an array (or cable/card/etc) then
you're running completely unmirrored for the entire time it takes to fix
the failure plus remirror - and remember that during a remirror is the
most likely time for a disk to fail. 

I'm actually installing 22 machines for a customer in the next few weeks
which will be setup exactly like this (running Sun Cluster, where the
rules state that you must mirror between two arrays)

  Scott