Testing out snapshots in Apple’s next-generation APFS file system

New file system announcements don’t happen every day. While it seems like everything else in technology is on ever tightening cycles of iteration, file systems remain the fine wine that takes some time. A file system from Apple on the other hand is more like a comet sighting.

So the excitement around their new APFS file system seems justified for its rarity if nothing else.  The biggest feature for most users will be snapshots, which APFS makes great use of. Sadly, it was not included in the APFS preview available to developers.

(Side rant: Apple File System? Really? That’s the best you could do Apple? Why not just go full egocentric and name is “File System”, like it’s the only one that exists. I guess it’s vaguely descriptive, in that only Apple devices will run it. But for a company supposedly known for creativity, it’s weak sauce.)

Adam Leventhal didn’t feel like waiting for snapshots in future MacOS updates, so he decided to find a way to take advantage of the fs_snapshot system call included in the most recent betas. He basically uses DTrace to reverse engineer how a snapshot is created. He then builds an app in an attempt to create an actual snapshot.

It’s a fascinating journey, with all the code, kernel processes and minor setbacks that you would expect.

Ars Technica comments:

Back in June, Apple announced its new upcoming file system: APFS, or Apple File System. There was no mention of it in the WWDC keynote, but devotees needed no encouragement. They picked over every scintilla of data from the documentation on Apple’s developer site, extrapolating, interpolating, eager for whatever was about to come. In the WWDC session hall, the crowd buzzed with a nervous energy, eager for the grand unveiling of APFS. I myself badge-swapped my way into the conference just to get that first glimpse of Apple’s first original filesystem in the 30+ years since HFS.


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About the author

Rich Stroffolino

Rich has been a tech enthusiast since he first used the speech simulator on a Magnavox Odyssey². Current areas of interest include ZFS, the false hopes of memristors, and the oral history of Transmeta.

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