From: Scott Marlowe <scott.marlowe@gmail.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: Jesper Krogh <jesper@krogh.cc>
Cc: pgsql-performance@postgresql.org
Subject: Re: moving pg_xlog -- yeah, it's worth it!
Date: Thu, 11 Feb 2010 09:12:08 -0700
Message-ID: <dcc563d11002110812w236de811g930e464d29cb1c9d@mail.gmail.com> (raw)
In-Reply-To: <201002111129.o1BBTK518798@momjian.us>
References: <4B7139DD020000250002F0E9@gw.wicourts.gov>
<201002111129.o1BBTK518798@momjian.us>
On Thu, Feb 11, 2010 at 4:29 AM, Bruce Momjian <bruce@momjian.us> wrote:
> Kevin Grittner wrote:
>> Jesper Krogh <jesper@krogh.cc> wrote:
>>
>> > Sorry if it is obvious.. but what filesystem/OS are you using and
>> > do you have BBU-writeback on the main data catalog also?
>>
>> Sorry for not providing more context.
>>
>> ATHENA:/var/pgsql/data # uname -a
>> Linux ATHENA 2.6.16.60-0.39.3-smp #1 SMP Mon May 11 11:46:34 UTC
>> 2009 x86_64 x86_64 x86_64 GNU/Linux
>> ATHENA:/var/pgsql/data # cat /etc/SuSE-release
>> SUSE Linux Enterprise Server 10 (x86_64)
>> VERSION = 10
>> PATCHLEVEL = 2
>>
>> File system is xfs noatime,nobarrier for all data; OS is on ext3. I
>> *think* the pg_xlog mirrored pair is hanging off the same
>> BBU-writeback controller as the big RAID, but I'd have to track down
>> the hardware tech to confirm, and he's out today. System has 16
>> Xeon CPUs and 64 GB RAM.
>
> I would be surprised if the RAID controller had a BBU-writeback cache.
> I don't think having xlog share a BBU-writeback makes things slower, and
> if it does, I would love for someone to explain why.
I believe in the past when this discussion showed up it was mainly due
to them being on the same file system (and then not with pg_xlog
separate) that made the biggest difference. I recall there being a
noticeable performance gain from having two file systems on the same
logical RAID device even.
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To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, bruce@momjian.us, Kevin.Grittner@wicourts.gov, jesper@krogh.cc
Subject: Re: moving pg_xlog -- yeah, it's worth it!
In-Reply-To: <dcc563d11002110812w236de811g930e464d29cb1c9d@mail.gmail.com>
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