Where does Time Machine server store its backups?
Since OS X server is just an app that runs on top of the standard OS X, you would open the Time Machine system preference pane to see where the server itself is backed up and which files may be excluded. (This is exactly the same as non-server app Macs, but Time Machine knows how to kick off server data snapshots as needed.)

In my case, I exclude the large backups and back up the small backups all to the drive XXX Backup A.

Then you can see that each of the machines either back up to the service destinations of Small Backups or Large backups.



And the storage lineup for this server is: