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@oneit.com.au