PostgreSQL 7.4.3 Performance issues on OpenBSD

Hello,

I'm experiencing performance problems with 7.4.3 on OpenBSD 3.6, at
least I think so. It is running on a Xeon 3 GHz with 2 GB RAM.

I have a table with 22 columns, all integer, timestamp or varchar and
10 indizes on integer, timestamp and varchar columns.

The table got 8500 rows (but growing). I try to make an UPDATE on the
table with 7000 affected rows. This update takes about 2-6 seconds.

Has it to be that slow? I'm running the same query on MySQL or Oracle
databases faster on similar machines.

EXPLAIN ANALYZE UPDATE ... tells me:
QUERY PLAN:
Seq Scan on table (cost=0.00..286.57 rows=4804 width=146) (actual
time=405.206..554.433 rows=7072 loops=1)
Filter: (system_knoten_links > 3501)
Total runtime: 2928.500 ms

So that looks fine to me, except the runtime.

Without indizes the query is fast with 456 ms.
Trying to disable fsync to avoid some disc operations aren't helping.

Sincerely TIA,
Glenn