Re: Follow-Up: How to improve db performance with $7K?

Thomas F.O'Connell wrote:
> I'd use two of your drives to create a mirrored partition where pg_xlog
> resides separate from the actual data.
>
> RAID 10 is probably appropriate for the remaining drives.
>
> Fortunately, you're not using Dell, so you don't have to worry about
> the Perc3/Di RAID controller, which is not so compatible with
> Linux...

Hmm...I have to wonder how true this is these days.

My company has a Dell 2500 with a Perc3/Di running Debian Linux, with
the 2.6.10 kernel.  The controller seems to work reasonably well,
though I wouldn't doubt that it's slower than a different one might
be.  But so far we haven't had any reliability issues with it.

Now, the performance is pretty bad considering the setup -- a RAID 5
with five 73.6 gig SCSI disks (10K RPM, I believe).  Reads through the
filesystem come through at about 65 megabytes/sec, writes about 35
megabytes/sec (at least, so says "bonnie -s 8192").  This is on a
system with a single 3 GHz Xeon and 1 gigabyte of memory.  I'd expect
much better read performance from what is essentially a stripe of 4
fast SCSI disks.


While compatibility hasn't really been an issue, at least as far as
the basics go, I still agree with your general sentiment -- stay away
from the Dells, at least if they have the Perc3/Di controller.  You'll
probably get much better performance out of something else.


--
Kevin Brown                          kevin@sysexperts.com