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Re: vacuum in Postgresql 8.0.x slowing down the database

From: Vinubalaji Gopal <vgopal(at)abaca(dot)com>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: vacuum in Postgresql 8.0.x slowing down the database
Date: 2008-03-28 07:28:33
Message-ID: 20080327232833.4d84b68b@vinu-ubuntu.abaca (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 26 Mar 2008 13:02:13 -0700
"Joshua D. Drake" <jd(at)commandprompt(dot)com> wrote:


> The slowness is likely attributed to Vacuum's use of I/O. When vacuum
> is running what does iostat -k 10 say?

Seems to be higher than normal - here is the output with vacuum run
without the other queries and the default vacuum taking ~1 hr:

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          13.30    0.00    4.50   25.91    0.00   56.29
Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
md2            3356.94      2005.59     12945.45      20076     129584


avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          16.20    0.00    6.32   24.89    0.00   52.59

Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
md2             461.70       667.20      1512.00       6672      15120


I don't know if the output helps much since the vacuum took some time
and I lost more than half of my iostat -k screen output. (I scrolled up
- but got only some of the data)

If vacuum does affect the io what are the ways to reduce the io during
vacuum (the delay and cost parameter did not help that much - should I
consider reducing the cost even further)? Should I consider
partitioning the table?

Thank you.

--
Vinu

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