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

Things might've changed somewhat over the past year, but this is from
_the_ Linux guy at Dell...

-tfo

--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC

Strategic Open Source — Open Your i™

http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-260-0005


Date: Mon, 26 Apr 2004 14:15:02 -0500
From: Matt Domsch <Matt_Domsch@dell.com>
To: linux-poweredge@dell.com
Subject: PERC3/Di failure workaround hypothesis


--uXxzq0nDebZQVNAZ
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Mon, Apr 26, 2004 at 11:10:36AM -0500, Sellek, Greg wrote:
 > Short of ordering a Perc4 for every 2650 that I want to upgrade to RH
 > ES, is there anything else I can do to get around the Perc3/Di
 > problem?

Our working hypothesis for a workaround is to do as follows:

In afacli, set:

Read Cache: enabled
Write Cache: enabled when protected

Then unplug the ROMB battery.  A reboot is not necessary.  The firmware
will immediately drop into Write-Through Cache mode, which in our
testing has not exhibited the problem.  Setting the write cache to
disabled in afacli doesn't seem to help - you've got to unplug the
battery with it in the above settings.

We are continuing to search for the root cause to the problem, and will
update the list when we can.

Thanks,
Matt

--
Matt Domsch
Sr. Software Engineer, Lead Engineer
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com

On Apr 5, 2005, at 11:44 PM, Kevin Brown wrote:

> 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