In the last couple of days, Apple has revealed that the High Sierra installer will not convert its very popular Fusion Drives to the new APFS file system – yet.
In a note aimed at system administrators, Apple makes clear that the High Sierra installer will automatically convert startup volumes on SSDs to APFS, and that they “can’t opt out of the transition to APFS”. However, it also states crisply that “Fusion Drives and hard disk drives (HDDs) aren’t converted”.
Even more puzzling is the statement that Macs running Sierra will be unable to mount and read volumes which have been converted to or formatted as APFS: “For example, a USB storage device formatted as APFS can be read by a Mac using High Sierra, but not by a Mac using Sierra or earlier.”
Currently, Sierra can do so, using bundled beta-release APFS support. This implies that the release version of APFS in High Sierra is incompatible with the version included in Sierra 10.12.6, and that Apple doesn’t intend offering any update to Sierra which will enable compatibility.
If this note remains accurate, it represents two major blunders in the introduction of High Sierra and APFS.
First, there seems very little point in any Mac with a Fusion Drive (or hard disk) being upgraded to High Sierra. APFS is High Sierra’s big new feature, and without it the upgrade seems nugatory.
Second, anyone using a mix of Macs running Sierra and High Sierra will be wisest not to use APFS on removable drives, as the systems still running Sierra will be unable to access anything on them. For many organisations, that will make High Sierra inadvisable until all Macs can be upgraded to it.
I cannot understand why Apple wants to make High Sierra so unattractive at this late stage. Failure to offer APFS on Fusion Drives and hard disks indicates that High Sierra is being released before it is ready for much of the desktop Mac market. During the summer Apple recognised that APFS was not yet ready for use on hard disks, but has pressed ahead with its release regardless.
High Sierra looks like being Apple’s least popular major upgrade to macOS/OS X/Mac OS X, and could turn out to be an embarrassing failure.
I have now updated my advice on when to update to High Sierra in the light of this disastrous news.