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To: pgsql-performance@postgresql.org
Subject: Re: 7 hrs for a pg_restore?
References: <200802191303.58840.doug@hunley.homeip.net>
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From: Guillaume Cottenceau <gc@mnc.ch>
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Date: Fri, 22 Feb 2008 11:40:42 +0100
In-Reply-To: <13059.1203617372@sss.pgh.pa.us> (Tom Lane's message of "Thu\,
	21 Feb 2008 13\:09\:32 -0500")
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Tom Lane <tgl 'at' sss.pgh.pa.us> writes:

> Guillaume Cottenceau <gc@mnc.ch> writes:
>> I have made a comparison restoring a production dump with default
>> and large maintenance_work_mem. The speedup improvement here is
>> only of 5% (12'30 => 11'50).
>
>> Apprently, on the restored database, data is 1337 MB[1] and
>> indexes 644 MB[2][2]. Pg is 8.2.3, checkpoint_segments 3,
>> maintenance_work_mem default (16MB) then 512MB, shared_buffers
>> 384MB. It is rather slow disks (Dell's LSI Logic RAID1), hdparm
>> reports 82 MB/sec for reads.
>
> The main thing that jumps out at me is that boosting checkpoint_segments
> would probably help.  I tend to set it to 30 or so (note that this
> corresponds to about 1GB taken up by pg_xlog).

Interestingly, from a bzipped dump, there is no win; however,
from an uncompressed dump, increasing checkpoint_segments from 3
to 30 decreases clock time from 9'50 to 8'30 (15% if I'm
correct).

-- 
Guillaume Cottenceau