So i've done a Testmigration and this worked so far well:
1) I've rsync'ed from the current zimbra server (open source version 6.0) the /opt/zimbra directory to a testserver (same Os, same hostname) where i've installed the same zimbra 6.0 Opensource version. (
Moving ZCS to New Server - Zimbra :: Wiki).
After the rsync the "zmcontrol start" on the testserver failed. I had to run a ldap recover (
ldap id2entry.bdb has bad LSN) after that it started
2) Then i've upgraded on the testserver to Network edition 7.0 (simply runned install.sh).
Looks ok. Data is present and the important things seem to work on first sight.
So it worked for me so far pretty well
thanks