Much more to do than just rsync.
You used CCC to create the backup?
Then use CCC to restore the backup to a drive.
Choose the folder as a source and a drive as the destination.
CCC supports this. Here's a note from the app on the topic of backup up to a folder.
You restore the contents of the backup folder to the root of another volume in the future, and that volume would be bootable. If your goal is to create a backup that you can boot from right now, you should back up directly to the root of this volume or to the root of another HFS+ formatted volume.
Thanks for your reply. I tried this way, unfortunately this strategy failed. The second mac mini wasn't able to start. I guess, the reason is that the mac minis weren't identical. (which is not possible because of different MAC-adresses etc.) So I had to setup the server from scratch an migrate from backup.
Realizing that it is obviously not possible to restore a backup of "OS X Server" on an other machine (same hardware-configuration but different machines) I'm looking for a backup-strategy for my case / worst case, which means "total loss of hardware" an restore from backup.
May be time machine is an option. It works well for clients but I've no experiences with the osx server/timemachine combination.
Thank's so far …