How to judge if a backup process is perfect?

After this round of transfer of 2.7TB of files, I will stick with rsync for file level transfers from now on.

A few questions:

  • how to prevent spase qcow2 files become fully allocated after rsync?
  • when the file is not exist in target
  • when the target exist in target but needs update
  • how to make rsync work nicely with COW btrfs filesystem? So far, I googled and used this:
    rsync --inplace --info=progress2 --no-whole-file -a source/ btrfs/

I so far only run rsync interactively, I would like as much progress indication as possible, like which file is being compared, which file is being transmitted, how much changed of each file, etc. With --info=progress2, I only got this one line staus:
0 0% 0.00kB/s 0:00:00 (xfr#0, ir-chk=2025/18024)

What parameters can provide such progress indications while rysnc is running?