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Message-ID: <4C20C8E1.7060306@denninger.net>
Date: Tue, 22 Jun 2010 09:29:53 -0500
From: Karl Denninger <karl@denninger.net>
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To: Justin Graf <justin@magwerks.com>
CC: =?UTF-8?B?R3J6ZWdvcnogSmHFm2tpZXdpY3o=?= <gryzman@gmail.com>,
	postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: raid10 write performance
References: <AANLkTinbKXufTYhNuhNaOW2kWM-simIL3dg0uFX7Ij6g@mail.gmail.com>
	<4C20BD33.1040908@magwerks.com>
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Justin Graf wrote:
> On 6/22/2010 4:31 AM, Grzegorz Jaśkiewicz wrote:
>   
>> Would moving WAL dir to separate disk help potentially ?
>>    
>>     
>
> Yes it can have a big impact.
WAL on a separate spindle will make a HUGE difference in performance. 
TPS rates frequently double OR BETTER with WAL on a dedicated spindle.

Strongly recommended.

Be aware that you must pay CLOSE ATTENTION to your backup strategy if
WAL is on a different physical disk.  Snapshotting the data disk where
WAL is on a separate spindle and backing it up **WILL NOT WORK** and
**WILL** result in an non-restoreable backup.

The manual discusses this but it's easy to miss.... don't or you'll get
a NASTY surprise if something goes wrong.....

-- Karl

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Justin Graf wrote:
<blockquote cite="mid:4C20BD33.1040908@magwerks.com" type="cite">
  <pre wrap="">On 6/22/2010 4:31 AM, Grzegorz Jaśkiewicz wrote:
  </pre>
  <blockquote type="cite">
    <pre wrap="">Would moving WAL dir to separate disk help potentially ?
   
    </pre>
  </blockquote>
  <pre wrap=""><!---->
Yes it can have a big impact.</pre>
</blockquote>
WAL on a separate spindle will make a HUGE difference in performance. 
TPS rates frequently double OR BETTER with WAL on a dedicated spindle.<br>
<br>
Strongly recommended.<br>
<br>
Be aware that you must pay CLOSE ATTENTION to your backup strategy if
WAL is on a different physical disk.  Snapshotting the data disk where
WAL is on a separate spindle and backing it up **WILL NOT WORK** and
**WILL** result in an non-restoreable backup.<br>
<br>
The manual discusses this but it's easy to miss.... don't or you'll get
a NASTY surprise if something goes wrong.....<br>
<br>
-- Karl<br>
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