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Re: vacuum taking longer over time

From: "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net>
To: Enzo D'addario <enzo(at)pienetworks(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: vacuum taking longer over time
Date: 2005-06-28 04:55:17
Message-ID: 42C0D835.7000603@zeut.net (view raw or flat)
Thread:
Lists: pgsql-admin
Enzo D'addario wrote:

>Hi All,
>
>I currently have postgres 7.4.2 running on a dedicated server which has
>1GB RAM, a Pentium 4 2600 Mhz processor, uses ReiserFS filesystem and is
>running Debian stable.
>
>After approximately 1 month I have to dump & restore the database
>because vacuum time spirals out of control. To give you an idea of what
>I experience, when the DB is restored it takes 1 hour to vacuum, however
>by the time the restore is 30 days old it can take up to 6 hours. I
>never experienced such issues with earlier versions of postgres.
>
>The DB is approximately 6 GB in size and is vacuumed analyzed nightly
>because of a relatively high number of transactions per day. 
>
>Another thing that I noticed from the vacuum logs is that the total
>pages needed shortly after restore is approximately 17000 and ends up
>over 50000 by the time the restore is 30 days old. 
>
>Does this mean the DB is becoming fragmented?
>  
>

Not fragmented, but bloated.  Sounds like you need to vacuum more often 
and / or increase your FSM settings.

>Will upgrading to postgres 8.0 resolve this problem?
>  
>

No, I think a more agressive vacuum regiment and / or larger FSM 
settings will solve this even 7.4.  Lots of people either setup cron to 
hit their more active tables more often, or use pg_autovacuum.

Good luck.


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