Re: Regular disk activity of an idle DBMS

Hello,

>> after configuring a new home server with PostgreSQL 9.0.4, I observe some regular disk activity, even though the
serveris completely idle (disconnected from the network, no users but one logged in). There are very short write bursts
oncein about 3 seconds. 
>
> There are a couple of things that can cause unexpected disk activity:
>
> -autovacuum running in the background. Setting log_autovacuum_min_duration may help you determine when this is
happening.
> -checkpoint activity. Turning on log_checkpoints, as well as looking for changes in the pg_stat_bgwriter view, may
helpexplain if this is the case. 

I repeatedly looked at that view, but it did not change during at least three *minutes*, so there is probably no
unexpectedcheckpoint activity. 

> -Hint bit updates. Even if you are only reading from a table, in some situations write activity can be generated. See
http://wiki.postgresql.org/wiki/Hint_Bitsfor more information. 
> -Statistics collector updates. If the one logged in user is doing anything at all, they might be generating something
here.

I identified the most active process, at least twenty times more active than any other process on the system:

    postgres  3086  0.1  0.0  34688  2584 ?        Ss   03:11   1:16 postgres: stats collector process

So it's the statistics collector. However, there does not seem to be any database activity at all. I tried looking at
thenumbers returned by this query: 

    select datname, tup_returned, tup_fetched from pg_stat_database ;

Nothing changes there. When OpenFire, Courier-MTA and Apache are restarted, a few numbers change, but othrewise they
remainunchanged pretty long. There is no obvious activity that could trigger a disk write 20 times a minute... 

Andrej