When Time Machine starts a backup, does it somehow take a snapshot of the current state of the filesystem such that any changes made to files after the backup starts are not reflected in the backup? I'm wondering about self-consistency of Time Machine backups. Are Time Machine backups perfectly consistent?
In case it isn't clear what I'm saying, here's an example. Say I have three files in a directory, 'a', 'b', and 'c', and each of them is 100 bytes in size. I start a Time Machine backup that is going to take a considerable amount of time...let's say an hour for argument sake.
In the next few minutes after starting the backup, I delete file 'a', append new information onto file 'b' making it 200 bytes in length, and create a new file 'd'. After the backup finishes, and I go in and look at the resulting snapshot, am I guaranteed to see three files 'a', 'b', and 'c', each of 100 bytes in length, and no file 'd'? Or is there no consistency guaranteed...how each of these files is backed up is a matter of when Time Machine actually backs up those particular files?
If someone thinks that Time Machine does take consistent snapshots, I would love to have a citation coming from Apple or someone who has rigorously tested to make sure this is the case. I have a particular reason to need to rely on such behavior.
TIA for any info!
PS: I think we are all running Monterey. We certainly all could be if it made a difference. I assume we're all running standard APFS setups.