Regular disk activity of an idle DBMS - Mailing list pgsql-general

Hello,

after configuring a new home server with PostgreSQL 9.0.4, I observe some regular disk activity, even though the server
iscompletely idle (disconnected from the network, no users but one logged in). There are very short write bursts once
inabout 3 seconds. This does not affect performance in any way, but I would like to know whether this is normal.
PerhapsI misconfigured something. With the 8.4.x version I used before, there were no such regular disk writes. 

I used the following approach to detect who is writing to disk:
http://www.xaprb.com/blog/2009/08/23/how-to-find-per-process-io-statistics-on-linux/This is what I obtained after about
3minutes of observation: 

    TASK                   PID      TOTAL       READ      WRITE      DIRTY DEVICES
    postgres             10437      10736          0      10736          0 dm-2
    md127_raid5            630        648          0        648          0 sdc, sda, sdb, sdd
    flush-253:3          29302        553          0        553          0 dm-3
    jbd2/dm-2-8           3411         62          0         62          0 dm-2
    flush-253:2           3835         35          0         35          0 dm-2
    jbd2/dm-3-8           3413         20          0         20          0 dm-3
    jbd2/dm-1-8           3409         12          0         12          0 dm-1
    flush-253:1            465         11          0         11          0 dm-1
    postgres             10434          9          0          9          0 dm-2
    jbd2/dm-5-8            789          6          0          6          0 dm-5
    postgres               850          4          0          4          0 dm-2
    bash                   400          4          0          4          0 dm-5
    flush-253:5            398          4          0          4          0 dm-5

These are my (non-default) PostgreSQL settings:

    # grep -Pv '^[ \t]*#|^[ \t]*$' /var/lib/postgres/data/postgresql.conf
    listen_addresses =
'::1,2002:53f0:5de8::1,2002:53f0:5de8:1::1,2002:53f0:5de8:2::1,2002:53f0:5de8:3::1,127.0.0.1,83.240.93.232,10.0.1.1,10.0.2.1,10.0.3.1'
    max_connections = 128                   # (change requires restart)
    ssl = on                                # (change requires restart)
    shared_buffers = 512MB                  # min 128kB
    temp_buffers = 64MB                     # min 800kB
    max_prepared_transactions = 128         # zero disables the feature
    work_mem = 16MB                         # min 64kB
    maintenance_work_mem = 128MB            # min 1MB
    max_stack_depth = 16MB                  # min 100kB
    effective_io_concurrency = 3            # 1-1000. 0 disables prefetching
    checkpoint_segments = 16                # in logfile segments, min 1, 16MB each
    log_destination = 'syslog'              # Valid values are combinations of
    autovacuum_max_workers = 8              # max number of autovacuum subprocesses
    datestyle = 'iso, dmy'
    lc_messages = 'cs_CZ.UTF-8'                     # locale for system error message
    lc_monetary = 'cs_CZ.UTF-8'                     # locale for monetary formatting
    lc_numeric = 'cs_CZ.UTF-8'                      # locale for number formatting
    lc_time = 'cs_CZ.UTF-8'                         # locale for time formatting
    default_text_search_config = 'pg_catalog.cs'

The machine runs ArchLinux. It is a standard piece of x86_64 commodity hardware. There are four SATA drives configured
asa RAID5 array. The file system is ext4. 

Is there an easy way to detect what exactly causes PostgreSQL to write these small amounts of data on an idle machine
ona regular basis? Stopping all daemons that connect to PostgreSQL (OpenFire, Apache, Courier-MTA) does not change
anything.Any hints would be very helpful. There is actually no performance or usability issue. I just want to
*understand*what is going on. 

Andrej