Confused about multiple backup sources


First off: Great software, I am using restic since many years :v:

I want to know about the benefits of having multiple backup sources (sources in terms of directories, not hosts) in one snapshot. For example: I want to backup A, B and C, I could run:

$ restic backup A B C

which would give me one snapshot containing all directories. I could also run

$ restic backup A
$ restic backup B
$ restic backup C

which would give me separate snapshots. Technically, for example the copy or forget command, I could merge then together (e.g. using tags), so I can only see a benefit of separating different directories. So what is the point in putting them in a single snapshot upfront?

How are you doing your backups? Do you split different directories into separate snapshots or merge them altother?

Let’s turn it around. What is the point of doing three separate backup runs of each their own directory, when all you want to do is back the state of these directories up at the point in time that you run the backup?

One potential use case for backing them up separately would be if you want to keep snapshots for the individual directories for different lengths of or frequencies of time. E.g. for A keep one snapshot for each month for the last year, but for B and C one snapshot per week for the last half year and one snapshot every day for the last week. If they were all in the same snapshot you can’t do that.

Generally speaking, one would simply add all the directories/paths that are to be backed up on one and the same system to one and the same backup run. Doing it differently would be due to some specific reason.