Message-ID: <4BE877BE.8000908@agliodbs.com>
Date: Mon, 10 May 2010 14:16:46 -0700
From: Josh Berkus <josh@agliodbs.com>
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To: pgsql-performance@postgresql.org
Subject: Re: 8K recordsize bad on ZFS?
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> That still is consistent with it being caused by the files being
> discontiguous. Copying them moved all the blocks to be contiguous and
> sequential on disk and might have had the same effect even if you had
> left the settings at 8kB blocks. You described it as "overloading the
> array/drives with commands" which is probably accurate but sounds less
> exotic if you say "the files were fragmented causing lots of seeks so
> our drives we saturated the drives' iops capacity". How many iops were
> you doing before and after anyways?

Don't know.  This was a client system and once we got the target
numbers, they stopped wanting me to run tests on in.  :-(

Note that this was a brand-new system, so there wasn't much time for
fragmentation to occur.

-- 
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com