Since this is a Mac OS X Server thread, I assume you are running one of the Server versions of Mac OS X.
With the introduction of Mac OS X Server Lion, the MySQL database was replaced with PostgreSQL. Further, all of the served features, the Wiki, Chat, etc., went from being stored in separate MySQL instances to a single PostgreSQL instance. Unfortunately, to the Time Machine process, the PostgreSQL data store presented as a single file. Thus, whenever one of the served features updated its data, the entire PostgreSQL data store presented as a new version of this (potentially large) file to Time Machine. An arbitrarily small change in content would therefore trigger a backup of a new version of the entire data store by Time Machine. This was impossibly inefficient. It would also fill the Time Capsule or sparceimage prematurely.
Thus, Apple chose to have Time Machine skip the PostgreSQL data store entirely. Thus, if you lost the PostgreSQL data store, you could NOT recover using Time Machine. Unfortunately, the designers of the Mac OS Server Lion software did not adequately inform Apple's customers or Apple's support arm, as I unfortunately learned after upgrading to Lion Server. The support people made a heroic effort, which came to no avail.
Thus, I would not recommend using Time Machine to back up Mac OS X Server unless for some reason you do not need to restore the PostgreSQL data, in which case you probably don't need Mac OS X Server at all.