[Linux-cluster] GFS performance problem

[FM]

Hello,

Here is my setup :
RedHat Enterprise 4 (update 3).
5 web servers connected to a 600 GB  GFS (noatime) on a SAN.
On the GFS : all web sites ROOTS and httpd logs files
All web servers are writing to the same log. No problem here.

The prob is with rsync. When writing on the GSF it is very very slow !
(40 % slower when we are lucky :) )

lots of question :
*) could it be because if I have 1 GFS for the heavy write on the log
and another GFS for the websites' files ?
*) expect for the noatime, is there other technic to speed up GFS ?
*) Can several webserver access EXT3 FS (read only) when only on other
server have RW access to it ?
*) is there a options to tune rsync when using GFS ?
*) we are using DLM as the locking system. All servers are connected
with Gb RJ45. Is DLM using the network to manage the lock. And if it is
the case, could my problem come from the network latency ?

As I said, lots of questions here :)