The executive has ostensibly confirmed the development via an email response, obtained by MacRumors, to a reader inquiry seeking details on the state of APFS and Fusion Drives.
“We intend to address this question very soon,” Federighi said in an email exchange with a MacRumors reader. The publication did not say whether or not Craig’s email is genuine.
According to an Apple support document, installing macOS High Sierra on your flash storage device automatically converts that volume to APFS. Fusion Drives are not converted to APFS.
Fusion Drive marries a traditional hard drive to an all-flash storage. This hybrid drive system presents itself to the user as a logical volume with the space of both drives combined.
Because Mac Fusion Drives (as well as traditional hard disk drives and non-Mac volumes) aren’t converted, and you cannot opt out of the transition to APFS, modern iMac and Mac mini computers that have Fusion Drives cannot currently use them as boot drives.
Fusion Drive compatibility may be added to APFS in macOS 10.14 this fall given that support for it is missing in the current macOS 10.13.5 beta and WWDC 2018 is just around the corner.
As AppleInsider watchfully observes, Federighi’s email is the first time that anyone inside Apple has actually addressed the APFS issue with Fusion Drives.
ADVISORY: Migrating your Mac to APFS
APFS is Apple’s modern file system designed for flash storage that sports native encryption, fast operations, easier backups, better responsiveness when moving large files and more.
iDownloadBlog has detailed the key APFS features at length.
Originally announced in June 2016 at Apple’s worldwide developers conference, APFS has replaced the decades-old HFS+ on iOS devices following the iOS 10.3 software update. Macs were upgraded to APFS with macOS High Sierra 10.13, which released last September.
APFS is also the default file system on Apple TV and Apple Watch.