Networked TimeMachine backups can use APFS

[haralds]

I just confirmed that networked TimeMachine backups use APFS in the same way as they would work on a local APFS disk.
APFS TimeMachine protocol has been completely reworked to use snapshots instead of hard links - faster and much more reliable.
TimeCapsule also works with this, since networked backups are encapsulated in sparse volumes on the underlying file system.
You do need to create a fresh backup after upgrading to Big Sur.
This does not change the implicit limitations of network speed and Apple's SLOW SMB protocol. But the nice part with networked TimeMachine is that it just worked in the background even during machine "nap" time.

 

[hobowankenobi]

Good to know.

The big test, for me...will be how reliable is it over the long haul. The last time used TM to back up network-attached Macs...the backups eventually became corrupt, losing all history and requiring staring over.

It was nearly impossible to test, as it was an occasional problem (several times it worked without issue for months, before failing). Seemed more frequent on wifi vs. wired, but no proof of this). This was on 10.14 as I recall, with similar problems on older OSes.

Hopefully, that has all been resolved. While TM is still lacking a few features, what is there is pretty great. I may have to test again...

 

[haralds]

When you look at how HFS+ works, it's quick to see that it becomes a tortuous collection of millions if hard links. Fine at the time of drive with a few GB, but insane when using TB. Backing up about 6 systems in my household I found that at least one backup would corrupt every one or two months.
I saw this more on a Mac mini running as a server than an actual AirPort TimeCapsule (modified with a 10TB disk.) But the latter is slow.