On 10/05/2020 12:07, Steven Davies wrote: > The original goal for my script was to answer the question "why does > qgroups show this snapshot has so much exclusive data?". I keep a record > of the qgroups reported exclusive sizes over time and occasionally check > whether backups or snapshotting need to be reconfigured. I figured that > a list of files and their exclusive extent sizes would show what is > contributing the most to the exclusive data shown by qgroups. Ah. In my case I have found the notion of "exclusive" to be useless. I don't use qgroups but I have on-disk snapshots of pretty much every subvolume so nothing is really exclusive. However, I do like to be able to answer questions like "if I was to remove these three old snapshots, how much space would be freed", and the other examples in the README for my scripts. Still, I am very interested to see how you get on -- my scripts only use FIEMAP today (effectively, using filefrag(8)). I am seriously considering, after I switch to using the Python library, building a userspace database of extent usage for files and directory trees so that the queries can be fast. The challenge, then, is to maintain it. It would, again, be very much like a usermode version of qgroups.
