From: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
---|---|
To: | Vlad Bailescu <vlad(at)mojitosoftware(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Unusually high IO for autovacuum worker |
Date: | 2013-02-01 13:27:58 |
Message-ID: | 1359725278.85293.YahooMailNeo@web162901.mail.bf1.yahoo.com |
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Lists: | pgsql-general pgsql-hackers |
Vlad Bailescu <vlad(at)mojitosoftware(dot)com> wrote:
> Because of our application stack (Hibernate ORM) we use a
> before_insert trigger to insert rows into the right partition and
> in the master table and then an after_insert trigger to delete
> them from master table (we need the original insert to return the
> inserted row info). This means the master table becomes quickly
> populated with dead tuples and triggers the autovacuum frequently
> (we are using default settings for autovacuum).
>
> After upgrading our DB from 8.4 to 9.1 (and moving from Debian 6
> to Ubuntu 12.04) we noticed a large increase in IO and traced it
> back to auto vacuum: iotop and collectd report bursts of 4-6M/s
> taking 90 seconds followed by a 30 seconds pause. That's a lot of
> data to chew on especially since the master table is only a
> couple of megabytes (indexes included).
>
> Can anyone please explain why this is happening and how we can
> get around it?
It sounds like it could be an issue which will be fixed in the next
minor release:
If this is the issue, a periodic manual VACUUM of the master table
should help for now. When 9.1.8 is released you might want to
upgrade without a lot of delay, and see if you are then OK without
the manual vacuums.
-Kevin
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