CMS update affects service desk?

Hello everyone, my case is as follows: 

 

I have a server with CMS 7.1 on another server this database (CMDB) and database service desk, on another server is the application service desk, in total I have 3 servers, I need to update the CMS version 7.5, the service desk will look affected or upgrade is transparent? or that considerations and precautions should I take? thank you very much