to fsync or not to fsync

Hello there, I'm trying to make sure my postgres 7.4 is running as fast
as it can in my box.
My hardware configuration is:

HP ML-350G3
Dup processor XEON 2.8
Three U320, 10000 rpm disks, RAID-5
HP 641 Raid Controller.
1GB RAM

My Software config is:

RedHat 7.3 - 2.4.20-28.7smp Kernel, reporting four processors because of
hyper threading.
Postgres 7.4
Data directory is on a ext3 journaled filesystem (data=journal)
Log directory is on another partition.
It is to be a dedicated to databases server, this means there are no
other heavy processes running.

My tests with pgbench with fsync turned off:

[root(at)dbs pgbench]# ./pgbench -U dba -P 4ghinec osdb -c 10 -s 11 -t 1000
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 1
number of clients: 10
number of transactions per client: 1000
number of transactions actually processed: 10000/10000
tps = 408.520028 (including connections establishing)
tps = 409.697088 (excluding connections establishing)

with fsync turned on:

[root(at)dbs pgbench]# ./pgbench -U dba -P 4ghinec osdb
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 1
number of clients: 1
number of transactions per client: 10
number of transactions actually processed: 10/10
tps = 43.366451 (including connections establishing)
tps = 44.867394 (excluding connections establishing)

I did a lot of these tests and results are consistent. Now then, without
fsync on I get a
1000% improvment!!!!

Questions now:

1) since I'm using ext3 with data=journal, do I need to use fsync=true?
2) Is there not a problem with RedHat? should fsyncs asked by postgres
to redhat be such a burden?
3) Any other tests you would suggest me to do?

thank you all

Rodrigo Filgueira Prates
IT(at)CINTERFOR/OIT
http://www.cinterfor.org.uy