One of the coolest developments from WWDC was the formal introduction to Apple’s new APFS file system. Hoping to correct HFS+ technical debt and growing pains, APFS looks to make Time Machine’s, iOS’s, and, most likely, your life easier.
APFS is looking to the future, and is designed fully around flash storage. Its notable features include enhanced encryption, better performance, all new snapshotting, and a smaller disk footprint. The testing releases currently don’t include compression, but its thought by many that compression will be added by the time it ships (the panel at WWDC agreed it was a useful feature.) APFS contains nearly all HFS+ features, making migration, in theory, easier and less error prone (in fact, an APFS volume can contain an HFS+ volume).
Encryption is particularly well supported, with the flagship feature being multi-key encryption (which currently doesn’t work in the Beta.) Metadata, files, and sections of a file can all be encrypted with different keys – especially useful for iOS.
Another useful feature for on-site service is the ability to securely wipe a drive instantly. The more paranoid, or law bound of us may still opt for a full wipe, but the new feature encrypts the system with a random, secure key. Of course, you’ll have to place trust in Apple’s implementation, but it looks to serve well for most casual users looking to sell a computer or device.
One of the most interesting performance related features is IO QoS. Separate from the system scheduler, this allows background processes to not interfere with IO bound GUI applications currently active.
Interesting, and possibly baffling to some users, is the built in de-duplication. If a file exists twice on the device, it will not be duplicated on disk. This can lead to a case where a file is emptied from the trash and no space is freed. Apple may provide some UI for this case, but this caveat currently exists.
As APFS doesn’t currently support file checksums (and likely won’t), a corruption in the original file will corrupt all de-duped copies. Apple’s response is that their hardware is of high quality and doesn’t require checksumming of files, but with the high number of aftermarket drives in the wild, this may be an issue for a small amount of people. (A small win for aftermarket drives is the inclusion of TRIM.)
Of note is the lack of hard links, currently. This may break some software which relies on them, and Time Machine is currently not functional with APFS for this reason. Snapshotting is built into APFS, so expect an updated Time Machine soon. In addition, the depreciated AFP is no longer supported on APFS volumes.
Want to play with APFS? Be warned that not all features and tools work currently (the flag, –IHaveBeenWarnedThatAPFSIsPreReleaseAndThatIMayLoseData, humorously highlights this), but the preview is stable enough for most day-to-day activities. Check out Developer Preview 10.12 (with the usual warnings of running a beta OS), or wait until the estimated ship date of 2017.
Many thanks to these helpful articles, which provide wonderful continued reading into the nitty gritty of APFS;
http://arstechnica.com/apple/2016/06/a-zfs-developers-analysis-of-the-good-and-bad-in-apples-new-apfs-file-system/
https://developer.apple.com/library/prerelease/content/documentation/FileManagement/Conceptual/APFS_Guide/Introduction/Introduction.html