What should be part of Collaborator backup?

We currently backup up the SQL Server database, but I am also wondering if there is a need to back up the following:

• Program Files\Collaborator Server\tomcat\collaborator-content-cache
• Program Files\Collaborator Server\tomcat\conf\Catalina\localhost\ROOT.xml

Would like to know what others are backing up, in case the server needs to be restored (it it gets corrupt) or duplicated (e.g. test server)