You know, I don't think that your advice to not use NAS is helpful and is rather condescending. I have been using a Synology NAS for Time Machine backups and also for file storage for some time now. I have an iMac, 2 x Macbook Pro, 1 x Windows 7 and Raspberry PI connected and using the NAS perfectly well. The 3 Macs use Time machine both wired and wireless. Admittedly third party device manufacturers should be testing with a new OS X release but for Apple to remove interfaces for legacy support without warning is, quite frankly, ridiculous. They, and Creative Labs, did the same thing with the USB support for audio interfaces at the release of El Capitan. Now, Creative support appear to have ignored completely the requests for updates to be compatible. I had to purchase a new Steinberg Audio Interface to get decent sound fro my iMac and am keeping my fingers crossed that it will still work with Sierra when I upgrade from El Capitan. I am a recent (well, 6 years ago and I'm 68 now) convert to Apple from Windows with absolutely no regrets. Also iPhone and iPad. The whole experience is truly much better than Windows but I'm not one of those Apple users that say that Windows is worthless. Just to mention Ikrupp's sage advice, how many of us have spare Mac to use as a test system and where would you look to check compatibility? Anyway, enough whingeing, I'm off to do a 2nd copy of a backup before upgrading. Wish me luck.