Re: Background writer underemphasized ...

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Background writer underemphasized ...
Date: 2008-04-16 19:55:51
Message-ID: Pine.GSO.4.64.0804161546310.27404@westnet.com
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On Wed, 16 Apr 2008, Bill Moran wrote:

>> bgwriter_delay = 10000ms # 10-10000ms between rounds
>> bgwriter_lru_maxpages = 1000 # 0-1000 max buffers written/round
> Have you watched closely under load to ensure that you're not seeing a
> huge performance hit every 10s when the bgwriter kicks off?

bgwriter_lru_maxpages = 1000 means that any background writer pass can
write at most 1000 pages = 8MB. Those are buffered writes going into the
OS cache, which it will write out at its own pace later. That isn't going
to cause a performance hit when it happens.

That isn't the real mystery though--where's the RAID5 rant I was expecting
from you?

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD

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