I think I’ve seen automatic compact after delete. If it happened, it might have used up the last little space.
Transition from delete to compact might be here. I suggest seeing if –no-auto-compact stops the filling. Increasing logging, e.g. (for recent Duplicati) –console-log-level=Information will show the action such as:
2018-10-28 13:02:02 -04 - [Information-Duplicati.Library.Main.Database.LocalDeleteDatabase-CompactReason]: Compacting not required
2018-10-29 13:01:24 -04 - [Information-Duplicati.Library.Main.Database.LocalDeleteDatabase-CompactReason]: Compacting because there are 52.41 MB in small volumes and the volume size is 50.00 MB
2018-10-29 13:05:05 -04 - [Information-Duplicati.Library.Main.Operation.CompactHandler-CompactResults]: Downloaded 22 file(s) with a total size of 117.33 MB, deleted 44 file(s) with a total size of 117.49 MB, and compacted to 4 file(s) with a size of 74.83 MB, which reduced storage by 40 file(s) and 42.65 MB
or the actual uploads that claim the last space, so that we can better observe what was happening then…
Sorry I missed that statement before suggesting that plan. So it’s a physical drive, thus resizing is also out?
I see you’re already getting the quota warning I’d referenced. The default --quota-warning-threshold is 10%.
The best outcome would be if --no-auto-compact helps. If not, the “migration” might be an option, especially convenient (for speed reasons) if move can be done within the NAS instead of having to go over a network.
A tricky technical maneuver would be to try to take advantage of information here to see what files could be sacrificed, knowing the next backup will fix things. On Windows, you’d need --unencrypted-database to look.
Another tricky technical maneuver is to try to delete the products of the last failed backup, however the risk there is that a compact will typically package old data into new files which might then be deleted by mistake. Current situation is different because the uncompleted delete command already said to delete old versions.
How about looking at the restore dropdown to see if that actually did such a heavy trim. If not, maybe trim it more lightly for starters (use higher –keep-versions), add --no-auto-compact, and try to get heavier logging.