Is there any hope that Time Machine might get reworked with APFS?

dwaite · on July 7, 2018

portions of time machine already have been (local backup uses snapshots, and is ridiculously simpler as a result).

Proper Time Machine "v2" is a bit more complex (basically a rsync clone based on local and remote snapshots), but still way simpler than the current "v1" method, which builds its own change table from fsevents and has to cope with a lack of snapshots in HFS+.

They can't use APFS as a Time Machine "v1" store because the unique feature of HFS+ to support directory hard-links did not carry over to APFS. Migration of a v1 to v2 volume would be a fun exercise in translations (folder hierarchy collapsed to volume snapshots, and differing crypto approaches for encrypted backups).

I suspect they are trying to get APFS in an evolutionary "stable" place so they can publicly document it with the iOS 12/macOS Mojave/etc releases - the changes they are making to support HDDs and Fusion drives this year are likely a big internal evolution.

I also suspect Apple is just not in a rush to move time machine over - it already works, has a surprising amount of integration across the OS for backup/recovery, and people tend to value their backups working vs using the newest technology.

Eventually, my belief is they will roll out Time Machine v2 and leave v1 (on HFS+) only supported for restoration. Just like with v1 today, non-APFS volumes will get a sparse bundle disk image to hold the APFS data. But they will wait until they have a strategy to migrate the external volumes and disk images.

cmurf · on July 7, 2018

There is definitely hope, it could turn out to be empty hope but... APFS has a lot to offer Time Machine as the hackery needed to get it to work on JHFS+/HFSX is tomfoolery at this point. At the least APFS has metadata checksums, and adding on an optional csum tree for data is not difficult for Apple to do. They already do COW with APFS so all that's needed is a separate tree for data csums. And then they have snapshots instead of hardlinks; or reflinks instead of hardlinks. I think it'll happen eventually as the deadweight of supporting HFS+ catches up with them.