@olivierlambert @florent thank you for the suggestions.
So far I have attempted to do the following:

1. Remote backup to NFS
2. Remote backup to NFS target which is connected to another storage server using iSCSI
3. Move the VM from one SR to another (on a completely different pool)
4. Copy the VM to another pool

Unfortunately, my VM size is not reducing.

@florent said in Backup size larger than it should be:

thin mode doesn't allocate space that is not needed. But once allocated, they stays there.

This looks like an answer to me.
In the worst-case scenario, I will have to recreate the VM and copy the data onto it

@tjkreidl I had no other storage repository connected to that host, so I had to attempt to move it to another host, which has its own storage repository. Unfortunately, the VM/Backup size is still nearly 190GB.

@tjkreidl I can't see any hidden snapshots, only a single snapshot created by the delta backup.
I will try moving the VM to another host, thanks for the advice.

@tjkreidl Thank you for your reply.
The local SR is only using 21% of the storage, so it has plenty of room to breathe. I have tried running sr-scan from the CLI and by using "rescan all disks", but with no luck.
What I have noticed though is that there is a base copy of the VM that appears to consume space on the local SR:

I have found the following article: https://xcp-ng.org/forum/topic/6719/deleting-snapshots-and-base-copies/11 but when I go to the Advanced tab of the local SR, it doesn't show any VDIs to be coalesced.
Reclaim free space option doesn't work for me as I'm getting the following error (possibly because the SR is used with HDDs not SSDs):

Trim on [8b69e781-0ece-595b-aa5b-832c79bfbec8] not supported

Hello,

I'm currently facing an issue while backing up a VM to a separate host using NFS. The problem lies in the backup size, which is showing as 190 GB, even though the VM contains only almost 20 GB of data.

Here are some additional details:

Initially, the VM had 190 GB of data, but I moved it elsewhere, reducing the data size to 20 GB.
After reducing the data size, I deleted the previous backup, ran the backup job again, and ended up with a 190 GB backup.
The VM is stored on a thin-provisioned SR, and its VDI size is 200 GB.
The root partition of the VM uses the XFS filesystem with LVM.
The backup job is configured as a Delta Backup.
The target server utilizes the EXT4 filesystem with LVM.
Interestingly, I have another VM with a similar setup (same filesystem and backup job), but it behaves as expected. This VM has a VDI size of 50 GB, contains 8 GB of data, and the backup size is 8 GB.

I'm puzzled as to why this is happening and would appreciate any insights.

Thanks in advance.