Hello,
after configuring a new home server with PostgreSQL 9.0.4, I observe some regular disk activity, even though the server is completely idle (disconnected from the network, no users but one logged in). There are very short write bursts once in 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 help explain 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 unexpected checkpoint 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_Bits for 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 the numbers 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 remain unchanged pretty long. There is
no obvious activity that could trigger a disk write 20 times a minute...
Andrej
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