Incremental backups all the same size as full on storage

I have set up image backups of two Hyper-V VMs (both are Linux), using the trial version of the Hyper-V client, yet I see in the GUI that all the backups are the same size for both full and incrementals:

It’s recorded as the same size for each saved file:

The backup log shows that CBT is in action and that during incrementals the amount of data is much smaller:

(UrBackup Server on Windows, 2.5.31)

Am I missing something?

I’m still seeing this behaviour and getting concerned by the fact that a backup of a small 60GB server after a few weeks is seemingly now occupying 2TB of backup storage.

Can anyone explain this to me? Thanks.

You don’t mention more than the server is running on windows. If the backup storage is on ntfs, I don’t think you can use incremental backups that way, but I could be wrong.

The storage is ReFS, plain simple volume without any deduplication or compression.

ok? then… I’m confused.

I might be wrong, but isn’t that exactly what you are trying to achieve?

When enabled, Data Deduplication optimizes free space on a volume by examining the data on the volume by looking for duplicated portions on the volume
Data Deduplication Overview | Microsoft Learn

edit. deduplication works on ntfs too, I was wrong.

On ReFS it uses reflinks to create clones of files. So each file won’t take up the full size, only the changed parts in the file.

See Block cloning on ReFS | Microsoft Learn

(The problem with ReFS is that this cannot be combined with compression compared to btrfs)

Thank-you for the explanation, just a shame Windows itself doesn’t make this clearer - I’m not worried about compression just as long as the reflinks are working as expected.