thx to you guys I finally configured my cluster:
2 sles10 sp3 + oes 2
edir, iManager, nss, ncp,... .
Both servers are connected to a iscsi-target. the vol is now mounted on server1. if i kill server1 the volume is correctly mounted on server2 - so everything is fine.

now I'm wondering... 2 questions:

1. what happens if while the volume is unmounted on server1 and mounted again on server2 a user is writing data to the volume?

2. do the client automatically reconnect?