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

On Wed, Aug 17, 2011 at 1:55 PM, Ogden <lists(at)darkstatic(dot)com> wrote:

>
>
> What about the OS itself? I put the Debian linux sysem also on XFS but
> haven't played around with it too much. Is it better to put the OS itself on
> ext4 and the /var/lib/pgsql partition on XFS?
>
>
We've always put the OS on whatever default filesystem it uses, and then put
PGDATA on a RAID 10/XFS and PGXLOG on RAID 1/XFS (and for our larger
installations, we setup another RAID 10/XFS for heavily accessed indexes or
tables). If you have a battery-backed cache on your controller (and it's
been tested to work), you can increase performance by mounting the XFS
partitions with "nobarrier"...just make sure your battery backup works.

I don't know how current this information is for 9.x (we're still on 8.4),
but there is (used to be?) a threshold above which more shared_buffers
didn't help. The numbers vary, but somewhere between 8 and 16 GB is
typically quoted. We set ours to 25% RAM, but no more than 12 GB (even for
our machines with 128+ GB of RAM) because that seems to be a breaking point
for our workload.

Of course, no advice will take the place of testing with your workload, so
be sure to test =)