Image backup reporting wrong size

I have Urbackup installed in a jail in Truenas Core and enabled ZFS for both “file” backups and “image” backups.
As a result, incremental “file backups” take very little space which makes sense because only the files that changed are backed up.

For incremental “image backups” the story is a bit different.
UrBackup is reporting that each incremental “image backup” take almost a much space as the Full “image backup”. This doesn’t make any sense because in an incremental backup only the “blocks” that changed since the last full backup are supposed to be saved.

However, according to Truenas, the incremental “image backups” are taking much less space than what Urbackup is reporting.


Urbackup reports that the “Image backups” are using about 683.12 Gb while truenas indicates that they are using about 277.85 Gb which is a substantial difference.

It seems that Urbackup is properly making the incremental image backups but reporting the wrong storage size for them.

Is there a setting I’m missing that may be making Urbackup to report the wrong storage size?
Or, is this a bug?
If so, how can i report it?

As a side note, the client is using “Change block tracking”

and the server is set to use “Raw copy-on-write file” as the image backup file format.


Not even to let me know how to report a bug?

I’d say this goes more into the feature request direction. Basically it’d need to call ZFS to get this data.

With btrfs I’m always running without quotas, so this is not calculated.