Re: Raid 5 vs Raid 10 Benchmarks Using bonnie++

> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-
> owner@postgresql.org] On Behalf Of Greg Smith
> Sent: Wednesday, August 17, 2011 3:18 PM
> To: pgsql-performance@postgresql.org
> Subject: Re: [PERFORM] Raid 5 vs Raid 10 Benchmarks Using bonnie++
> 
> On 08/17/2011 02:26 PM, Ogden wrote:
> > I am using bonnie++ to benchmark our current Postgres system (on RAID
> > 5) with the new one we have, which I have configured with RAID 10.
> The
> > drives are the same (SAS 15K). I tried the new system with ext3 and
> > then XFS but the results seem really outrageous as compared to the
> > current system, or am I reading things wrong?
> >
> > The benchmark results are here:
> > http://malekkoheavyindustry.com/benchmark.html
> 
> Congratulations--you're now qualified to be a member of the "RAID5
> sucks" club.  You can find other members at
> http://www.miracleas.com/BAARF/BAARF2.html  Reasonable read speeds and
> just terrible write ones are expected if that's on your old hardware.
> Your new results are what I would expect from the hardware you've
> described.
> 
> The only thing that looks weird are your ext4 "Sequential Output -
> Block" results.  They should be between the ext3 and the XFS results,
> not far lower than either.  Normally this only comes from using a bad
> set of mount options.  With a battery-backed write cache, you'd want to
> use "nobarrier" for example; if you didn't do that, that can crush
> output rates.
> 

To clarify maybe for those new at using non-default mount options.

With XFS the mount option is nobarrier. With ext4 I think it is barrier=0

Someone please correct me if I am misleading people or otherwise mistaken.

-mark