Backup size is severely overestimated

[hexagonrecursion]

Qubes OS version
Qubes release 4.0 (R4.0)

Affected component(s) or functionality
"Backup Qubes" wizard

Brief summary
On the page where you select which qubes to include in the backup the size of each qube is overestimated.

To Reproduce

1. Start the "Backup Qubes" wizard
2. On the initial page note the total backup size
3. Clink next 2 times
4. Compare total size to the one reported on the summary page

Expected behavior
A reasonably accurate estimate of the contribution of each qube to the backup size and the total backup size should be displayed.

Actual behavior
The size appears to be severely overestimated. In particular:

1. dom0 is reported to be tens of GiB in size
2. Any qube that is running at the time is reported to have a much bigger size than it actually has

Additional context
In case it matters: my primary pool is a btrfs-backed file-reflink. I understand that it is impossible to predict the effectiveness of backup compression. This issue in not about compression, but specifically about two wizard pages disagreeing on the backup size.

Relevant documentation you've consulted
none

Related, non-duplicate issues
none

[marmarek]

I guess it counts the size together with all previous and temporary snapshots, by summing them...

[rustybird]

Any downsides to changing get_disk_utilization() in qubesadmin.vm (and also the equivalent one in qubes.storage, which currently has no callers) to only sum up save_on_stop volumes?

Edit: On second thought, that would make it return 0 for all DisposableVMs, which is correct in backup VM selection but unhelpful in the VM tray widget and in qvm-ls.

[rustybird]

The way too large reported size of dom0 is because shutil.disk_usage() is called on the home directory, but this actually returns the usage of the whole mountpoint.

[github-actions]

This issue is being closed because:

• This issue is on the "Release 4.0 updates" milestone.
• Qubes OS 4.0 reached EOL (end-of-life) over one year ago.
• There has not been any activity on this issue in over one year.

If anyone believes that this issue should be reopened and reassigned to an active milestone, please leave a brief comment.
(For example, if a bug still affects Qubes OS 4.1, then the comment "Affects 4.1" will suffice.)

[rustybird]

Affects 4.2