Date: Wed, 16 Apr 2008 16:07:24 -0400
From: Bill Moran <wmoran@collaborativefusion.com>
To: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Background writer underemphasized ...
Message-Id: <20080416160724.7605ffdb.wmoran@collaborativefusion.com>
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In response to Greg Smith <gsmith@gregsmith.com>:

> 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?

Oh crap ... he _is_ using RAID-5!  I completely missed an opportunity to
rant!

blah blah blah ... RAID-5 == evile, etc ...

-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran@collaborativefusion.com
Phone: 412-422-3463x4023