I’ve used my Drobo 5D for Time Machine backups since 2014 (when purchased) with no issues. Due to the specifics of the Time Machine backup (lots of symlinks and custom permissions), it’s easier to reformat the Drobo instead of attempting to remove old backups by hand. That’s what I do on a regular basis when I run out of space on Drobo.
This time however reformatting attempt hangs forever. It says wait for 5 minutes before formatting is over and I’ve waiting 8 hours and nothing happened.
Disks have no bad sectors, though 2 of 5 had red “ultradma crc errors” indicator according to S.M.A.R.T. checks.
I’ve also tried removing 1 of the disks and that causes some kind of redundancy rebuild process (disk isn’t even formatted) and after finished doing reformat won’t do anything (still hangs).