From: Ralph Mason <ralph.mason@telogis.com>
To: 'Joshua D. Drake' <jd@commandprompt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Ever Increasing IOWAIT
Date: Fri, 18 May 2007 11:19:09 +1200
Message-ID: <012d01c798d9$c6d520d0$547f6270$@mason@telogis.com> (raw)
In-Reply-To: <464CDF0A.5050309@commandprompt.com>
References: <011b01c798d5$141365a0$3c3a30e0$@mason@telogis.com>
<464CDF0A.5050309@commandprompt.com>
Hi Josh - thanks for thoughts.
>
> This is Postgres 8.1.4 64bit.
>1. Upgrade to 8.1.9. There is a bug with autovac that is fixed that is
>pretty important.
We don't use pg_autovac - we have our own process that runs very often
vacuuming tables that are dirty. It works well and vacuums when activity is
happening. During busy time active tables are vacuumed about once a minute.
The 'slack' space on busy tables sits at about 100% (eg the table has 2X the
number of pages it would after a cluster) We use rows updated and deleted
to decide what to vacuum. Those busy tables are reasonably small and take
less than a second to vacuum.
Also, If it were a vacuuming problem why would a restart of the engine fix
it fully?
>
> Anyone have any ideas?
>
>Sure... you aren't analyzing enough. You are using prepared queries that
>have plans that get stale... you are not running autovac... You are
>cursed (kidding)..
The shape of the data never changes and we don't reanalyze on start-up so
suspect analyzing won't do much (although we do every so often).
We don't use prepared queries - just lots of functions - but like I said
above the shape of the data doesn't change. So even if postgres stores plans
for those (does it?) it seems like it should be just fine.
Thanks
Ralph
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To: pgsql-performance@postgresql.org
Cc: ralph.mason@telogis.com, jd@commandprompt.com
Subject: Re: Ever Increasing IOWAIT
In-Reply-To: <012d01c798d9$c6d520d0$547f6270$@mason@telogis.com>
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