Re: Vacuums taking forever :(

From: Andreas Wenk <a(dot)wenk(at)netzmeister-st-pauli(dot)de>
To: Phoenix Kiula <phoenix(dot)kiula(at)gmail(dot)com>
Cc: PG-General Mailing List <pgsql-general(at)postgresql(dot)org>
Subject: Re: Vacuums taking forever :(
Date: 2009-02-03 13:09:53
Message-ID: 49884221.1060400@netzmeister-st-pauli.de
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Phoenix Kiula schrieb:
> In my conf_pg, the autovacuum is on, so the DB should be (or I hope is
> being) regularly vacuumed.
>
> These are my settings:
>
>
> work_mem = 20MB
> temp_buffers = 4096
> authentication_timeout = 10s
> ssl = off
> checkpoint_warning = 3600
> random_page_cost = 1
> autovacuum = on
> autovacuum_vacuum_cost_delay = 20
> vacuum_cost_delay = 20
> autovacuum_naptime = 10
> stats_start_collector = on
> stats_row_level = on
> autovacuum_vacuum_threshold = 75
> autovacuum_analyze_threshold = 25
> autovacuum_analyze_scale_factor = 0.02
> autovacuum_vacuum_scale_factor = 0.01
>

Hi ,

just a quick thought. What is your maintenance_work_mem parameter set to? I think with
that lot Updates and Inserts this should not be too low ...

Cheers

Andy
>
> The autovacuum was clearly not enough, so we also have a crontab that
> vacuums the tables every hour. This is PG 8.2.9.
>
> These cron jobs are taking over 35 minutes for a vacuum! What's the
> use of a vacuum if it takes that long, and the DB performance is
> tragic in the meantime?
>
> I'd truly appreciate some thoughts from people with experience of
> vacuum management of highly available online databases. About 10-20
> million accesses for this one. Most are SELECTs. We have about 500,000
> INSERTs and about 800,000 UPDATEs. Just 11 tables, of which only one
> is like 10 million rows. Two are close to 500,000 rows, rest are
> really small. It is this 10 million row thing that's the worry.
>
> Thanks!
>
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