The upcoming release of Gluster 4.0 would require the users to upgrade systems from a possible set of 3.x series. It would be ideal to put together a matrix of the combination of client and server which lend themselves to easy upgrade. This matrix can be included in the documentation notes/section specifically pertaining to an upgrade.
Additionally, with the declared intent to discontinue the server RPMs for CentOS6 (due to Golang programming language run-time unavailability), it is likely that users would seek to standardize their operating infrastructures on a CentOS7 based deployment. Thus, a known good method or, a process that has been qualified would be needed for documentation.