There is a ton of good information and lengthy guides on the actual in-place upgrade process for Skype for Business, so no point regurgitating it here. Instead, I've provided a couple of gotcha and tips to help make your upgrade go a little smoother.
1. | Make sure you have at least 32GB of free diskspace before running the in-place upgrade. The installer will verify that as one of the pre-reqs too.  |
2. | Shutdown and restart the Powershell window. If you had the Lync Management Shell console open while your server was getting upgraded to SfB, make sure you shut down that window, and start a new SfB Management Shell window. The fancy new start-cspool and other new SfB command will not run in the old version of that shell (which has also been overwritten by new bits). |
3. | This one will hopefully be fixed in an upcoming release, but you MUST have the Windows Firewall Service running the first time you run start-cspool command after the upgrade is complete. The Windows Fabric seems to do a bunch of configuration updates at first launch, and if the Wnidows Firewall is not running, it will fail to start. On the console windows you will see the start-cspool command fail with something similar to this error.  Start-CsPool : An error occurred while making the HTTP request to https://****fe06.domain.com/LiveServer/UserPinManagement/FabricManagement/. This could be due to the fact that the server certificate is not configured properly with HTTP.SYS in the HTTPS case. This could also be caused by a mismatch of the security binding between the client and the server. ... ... Start-CsPool : Please make sure at least 2 machine(s) are in running or starting state to achieve fabric network ring quorum from the following machine list. Also makes sure Windows Fabric Host Service is running on those machines. ****FE06.DOMAIN.COM ****FE07.DOMAIN.COM ****FE08.DOMAIN.COM ... ... Not enough seed nodes are running. ,Microsoft.Rtc.Management.Hadr.StartOcsPoolCmdlet If you also look at the events under Microsoft-Windows-WindowsFabric, you will see it referring to FabricDeployer.FirewallManager.EnableFirewallSettings. Just start the Windows Firewall service, and let the Fabric do it's thing. After the pool is up, you can stop the service if you want to. |
4. | Check your back-end database versions to ensure they are at the proper versions. Run |
5. | Run the SfB Setup Wizard at the end on each FE to enable/disable all the new changes in the topology. |
6. | Run the Get-csServerVersion command and Congratulate yourself for a job well done :-)  |