Apple must have invested incredible resources on testing that internally, because that was a very risky move, and well outside the norm for filesystem development.
As an aside, this is one of the several unbelievably slick updates Apple has pulled off in its history, including:
- the switch to 32-bit clean addresses only (which was probably the most painful switch Apple ever did!) in System 7.6
- the switch to PowerPC (which caused fewer problems than the 32-bit clean switch!)
- the switch to Mac OS X
- the switch to Intel
- the switch to 64-bit on desktop
- the switch to 64-bit on iOS
Microsoft, (in most cases rightly) vaunted for backwards compatibility has had horrific snafus such as DOS 5 being the first version of DOS whose RESTORE program could read BACKUP files from the previous version of DOS.
(It's also worth noting that NeXT itself managed to support four runtime architectures with "quad fat binaries".)
I suppose that meant doing a small install in some virtual disk? I can't think apple put at risk anyone's data.
But then, that would not have been the same as actually testing the real hardware interface, would it?
[0] https://discussions.apple.com/thread/8073670?start=0&tstart=...
More relevant to the parent, though: the upgrade to APFS happened in iOS 10.3, not iOS 11. So whatever bug you may have had with iOS 11 probably have nothing to do with the file system.
http://www.techradar.com/how-to/ios-11-problems-how-to-fix-t...
https://www.forbes.com/sites/gordonkelly/2017/09/24/apple-io...
https://www.imobie.com/support/ios-11-problems-and-solutions...
https://www.gottabemobile.com/ios-11-problems-fixes/
https://www.macrumors.com/2017/09/25/ios-11-app-slowdowns-pe...
http://mashable.com/2017/09/21/apple-ios11-glitches/#Q72Ibvr...
http://www.iphonehacks.com/2017/09/ios-11-bugs.html
https://arstechnica.com/gadgets/2017/09/some-ios-11-issues-s...
https://www.tenorshare.com/ios-11/top-15-ios-11-update-probl...
http://www.independent.co.uk/life-style/gadgets-and-tech/new...
http://www.trustedreviews.com/news/ios-11-problems-3293849
https://www.usatoday.com/story/tech/columnist/2017/09/26/app...
http://osxdaily.com/2017/09/26/troubleshooting-ios-11-proble...
https://www.dailydot.com/debug/ios-11-bugs/
https://appletoolbox.com/2017/09/common-ios-11-problems-how-...
https://www.theregister.co.uk/2017/09/21/ios_11_screws_up_ou...
http://www.dailymail.co.uk/sciencetech/article-4922738/Apple...
http://www.mirror.co.uk/tech/apple-confirms-ios-bugs-issues-...
Should I go on?