analyzing postgresql performance for dbt-2

I'm running our DBT-2 workload against PostgreSQL 7.3.4 and I'm having
some trouble figuring out what I should be looking for when I'm trying
to tune the database.  I have results for a decent baseline, but when I
try to increase the load on the database, the performance drops.
Nothing in the graphs (in the links listed later) sticks out to me so
I'm wondering if there are other database statitics I should try to
collect. Any suggestions would be great and let me know if I can answer
any other questions.

Here are a pair of results where I just raise the load on the
database, where increasing the load increases the area of the database
touched in addition to increasing the transaction rate.  The overall
metric increases somewhat, but the response time for most of the
interactions also increases significantly:

http://developer.osdl.org/markw/dbt2-pgsql/158/ [baseline]
    - load of 100 warehouses
    - metric 1249.65

http://developer.osdl.org/markw/dbt2-pgsql/149/
    - load of 140 warehouses
    - metric 1323.90

Both of these runs had wal_buffers set to 8, checkpoint_segments 200,
and checkpoint_timeout 1800.

So far I've only tried various wal_buffers and checkpoint_segments
settings in the next set of results for a load of 140 warehouses.

http://developer.osdl.org/markw/dbt2-pgsql/148/
- metric 1279.26
- wal_buffers 8
- checkpoint_segments 100
- checkpoint_timeout 300

http://developer.osdl.org/markw/dbt2-pgsql/149/
- metric 1323.90
- wal_buffers 8
- checkpoint_segments 200
- checkpoint_timeout 1800

http://developer.osdl.org/markw/dbt2-pgsql/150/
- metric 1281.13
- wal_buffers 8
- checkpoint_segments 300
- checkpoint_timeout 1800

http://developer.osdl.org/markw/dbt2-pgsql/151/
- metric 1311.99
- wal_buffers 32
- checkpoint_segments 200
- checkpoint_timeout 1800

http://developer.osdl.org/markw/dbt2-pgsql/152/
- metric 1268.37
- wal_buffers 64
- checkpoint_segments 200
- checkpoint_timeout 1800

http://developer.osdl.org/markw/dbt2-pgsql/154/
- metric 1314.62
- wal_buffers 16
- checkpoint_segments 200
- checkpoint_timeout 1800


Thanks!

--
Mark Wong - - markw@osdl.org
Open Source Development Lab Inc - A non-profit corporation
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