extrem bad performance

Hi,

I operate a database server with postgres 7.3.2, 2 Xeon CPU's and 1 GB
Ram. The database-files reside on a local SCSI-HD, the system runs on
SuSE Enterprise Server 8.0.

The size of the dumped database is about 300 MB, the database is
vacuumed (-a -z) every night an reindexed every week.

The database server is used by a lamp applicationsserver over a 100 MBit
Network.

My Problem is, that the DB-Server is unbelievable slow!

I monitor the database with top. When a (small) query is executed, I see
the postmaster task for 2-3 seconds with 80-100 % CPU load. On other
systems with the same database but less CPU and RAM power, I see the
task for one moment with 2-8 % CPU load. The other systems behave normal
the speed is ok.

Also a restart of the postmaster brings no improvement.

The database grows very slowly. The main load comes from SELECT's and
not from INSERT's or UPDATE's, but the performance gets slower day by day...

I have no idea where to search for the speed break!

Stefan