Reply to thread

Not from Essentials to 2012 R2, but did an in-place upgrade from 2012 >> 2012 R2 a while ago without issues.

I suspect you need to copy some drivers after the upgrade, since those aren't included in 2012 R2. Got mine included in case you don't have access to a Win 8.1 client. Simply run server_bdasetup.bat on your Server 2012 R2 OS and you should be good to go.

Just make an image/backup of the disc before you do the upgrade, then you can always restore.