Postgres 9.1.4 - high stats collector IO usage

Hi,

I am running postgres 9.1.4 on Ubuntu 12.04 and the stats collector is
generating very high IO usage even when nothing appears to be happening
on the system.

I have roughly 150 different databases, each of which is running in 1 of
roughly 30 tablespaces. The databases are small (the dump of most is
are under 100M, and all but 3 are under 1G, nothing larger than 2G).

Previously iotop reported the disk write speed, at ~6MB / second. I
went and reset the stats for every database and that shrunk the stats
file and brought the IO it down to 1MB / second. I still think this is
too high for an idle database. I've now noticed it is growing.

ls -l /var/lib/postgresql/9.1/main/pg_stat_tmp/pgstat.stat
-rw------- 1 postgres postgres 3515080 Jul 28 11:58
/var/lib/postgresql/9.1/main/pg_stat_tmp/pgstat.stat

*<reset of stats> *

ls -l /var/lib/postgresql/9.1/main/pg_stat_tmp/pgstat.stat
-rw------- 1 postgres postgres 514761 Jul 28 12:11
/var/lib/postgresql/9.1/main/pg_stat_tmp/pgstat.stat

*<watch the file grow>*

ls -l /var/lib/postgresql/9.1/main/pg_stat_tmp/pgstat.stat
-rw------- 1 postgres postgres 776711 Jul 28 12:25
/var/lib/postgresql/9.1/main/pg_stat_tmp/pgstat.stat

In the 15 minutes since the reset, IO has nearly doubled to 1.6+ MB /
second.

FWIW, I just migrated all these databases over to this new server by
restoring from pg_dump I was previously experiencing this on 8.3, which
was why I upgraded to 9.1 and I also have another server with similar
problems on 9.1.

Any help would be sincerely appreciated.

David Barton dave(at)oneit(dot)com(dot)au