Re: high throughput storage server?

David Brown put forth on 2/23/2011 7:56 AM:

However, as disks get bigger, the chance of errors on any given disk is
increasing.  And the fact remains that if you have a failure on a RAID10
system, you then have a single point of failure during the rebuild
period - while with RAID6 you still have redundancy (obviously RAID5 is
far worse here).

The problem isn't a 2nd whole drive failure during the rebuild, but a
URE during rebuild:

http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162

I don't know if you've followed the recent "md road-map: 2011" thread (I
can't see any replies from you in the thread), but that is my reference
point here.

Actually I haven't.  Is Neil's motivation with this RAID5/6 "mirror
rebuild" to avoid the URE problem?

Incidentally, what's your opinion on a RAID1+5 or RAID1+6 setup, where
you have a RAID5 or RAID6 build from RAID1 pairs?  You get all the
rebuild benefits of RAID1 or RAID10, such as simple and fast direct
copies for rebuilds, and little performance degradation.  But you also
get multiple failure redundancy from the RAID5 or RAID6.  It could be
that it is excessive - that the extra redundancy is not worth the
performance cost (you still have poor small write performance).

I don't care for and don't use parity RAID levels.  Simple mirroring and
RAID10 have served me well for a very long time.  They have many
advantages over parity RAID and few, if any, disadvantages.  I've
mentioned all of these in previous posts.

-- 
Stan


-- 
Stan