If you converted a Fusion Drive to APFS during the macOS 10.13 High Sierra beta, we have some bad news: the initial release version of High Sierra that Apple plans to ship on 25 September 2017 will not officially support it. This unexpected announcement presumably comes due to problems discovered during the beta that the company hasn’t yet addressed. Apple recommends that you back up the Fusion Drive, reformat it using Mac OS Extended (HFS+), and restore it from backup. The support document implies that Apple will support APFS-formatted Fusion Drives in a later release of High Sierra.follow link
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Initial High Sierra Release Won’t Support APFS for Fusion Drives
Comments about Initial High Sierra Release Won’t Support APFS for Fusion Drives
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I was that man! I had greater or lesser amounts of trouble installing the betas on a Mac Mini with a Fusion drive: sometimes it took a long time trying to convert HFS+ to APFS before reverting; sometimes it managed the conversion; and sometimes it failed altogether. Later betas (applied after I had had enough of this and restored from Time Machine to a rebuilt HFS+ Fusion drive) did not even offer to make the conversion.
Ya, won't be updating to High Sierra anything soon on my iMac and MBP 15". I have installed it on two Macs so far and have tried it on mac mini without success. It stalls and says it closing apps but it never goes any further, but I think it's deeper than that since Sierra won't reboot or shut down with the normal menu under the Apple. I can kill it down through Terminal and on the login screen where you have the usual three options. Sleep, Restart, and Shutdown.
I installed the Beta on a Mac Mini with a hybrid drive system converted from a spinning HD system. I had no trouble installing the Beta however when I tried to drag and drop a file from one Finder window to another Finder would crash. It could be restarted with little effort but the problem was persistant. You can move and copy files by most other methods, but you can not drag and drop between two windows. I have reported the problem to Apple from two builds. I presume from the above artical that they have not been able to resolve the problem. Given that the main advantage of Mac OS was always drag and drop it would be stupid to release an OS that crashes when you use it. I will not be installing Mac OS High Sierra until I read a report from you or elswere that states that APFS now works on the Fusion drive system.