Today’s software updates from Apple are notable for a lot of reasons. macOS 10.12.4 gets Night Shift from iOS, I can now find my AirPods in the Find My iPhone app, there are the beginnings of a standard to control apps that nag you for reviews on iOS 10.3, Siri enhancements on watchOS 3.2, but the most important change is he first switch from HFS+ to APFS. APFS is Apple’s new file system for iOS, macOS, tvOS, and watchOS. It’ll be installed with the latest iOS update, and will come to macOS in the future.
File systems keep track of where your files are on a storage medium like a hard drive or SD card, and Apple has been using some variation of the same file system, HFS and HFS+, for the past thirty years.
APFS should be an improvement in performance and reliability because it is targeted towards modern computing devices that use flash memory instead of spinning disks, but it is going to be a little bit like pulling a table cloth out from under a plated dinner and table setting in order for the operating system to replace the file system on the devices during the update.
I made sure my iCloud backups were all up to date before starting the upgrade, you should too.