macOS and Time Machine backup
After weeks of problems with Time Machine - eg the calculation of the duration of a backup of just 1 Gb must be interrupted after three days - including an incident ticket at Apple which was not able to solve the issue (btw: Thank you for your help, time and assistance, even when you not found the root cause).
Each time when we attached a disk device to initiate a backup it starts to calculate the time and never came to an end. Today we found the root cause for this behavior:
An application (Disk Drill) created a subdirectory on the harddrive and created a very huge number of small files in that directory. We analyzed this using
sudo fs_usage -w |grep -i backupd |grep -i fsctl
and recognized that a lot of files located in
/System/Volumes/Data/.cleverfiles
where responsible for this misbehaviour. Excluding this directory from Time Machine solves the issue. Thanks to Mac O' Clock for the hints to solve this issue.