Hello,

Can you confirm which storage backend the affected VMs are using in Proxmox, and what disk format (RAW or QCOW2)?

Is the successful VM stored on the exact same storage and format as the ones failing?

I’m asking this because Veeam officially supports only certain storage backends — specifically file-based storages (like a directory with RAW/QCOW2 disks). If the VMs are stored on LVM-thin, ZFS, Ceph, or have iSCSI disks attached, Veeam will skip those disks and report them as “unsupported storage type”.

You can check this in Proxmox under VM → Hardware → Hard Disk to compare the storage/format of the working VM and the failing ones.

For reference, here’s the considerations and limitations doc:

https://helpcenter.veeam.com/docs/vbproxmoxve/userguide/limitations.html

Veeam Plug-in for Proxmox VE does not support backup of VMs that store their disks in the BTRFS and custom storage. All other Proxmox VE storage types are supported.

…

Veeam Plug-in for Proxmox VE does not support backup of iSCSI disks. If iSCSI disks are attached to a VM included into a backup job, these disks will be skipped from processing.”

Are the failing VMs using disks with BTFRS filesystem? This would not be supported, see this thread on the Veeam R&D forums: (5) BTRFS support dropped in 12.3.1.1139? - R&D Forums

Oh, ​@matheusgiovanini  beat me on that one 😅

Looks like we’re on the same page 🤣

Thanks for the quick response!

I double-checked all my VM’s and it looks like the format to all of them is “RAW”.  I grabbed a screenshot of just one VM as an example so as to not flood this thread.

I also need to backtrack on my original post, as it turns out the VM that backed up successfully was LVM and not iSCSI.  I noticed this when I was double-checking my setup.

So it looks like none of my iSCSI VM’s are backing up even though they are all RAW Format.

EDIT:  I read the article you linked, so now its my understanding that Veeam does not support iSCSI at all?  Or would there be an additional layer to the veeam setup to make it work?

For Clarity, the Backup that is successful is in the GB while those with warnings are in the MB.

My thought is for the ones with warnings, the VM Settings are being backed up just not the data that goes with them.

if iSCSI is not supported at all with veeam, i would figure i need to re-think backing up those Drives by another means while Veeam can still be used to save the VM Settings.  Just typing out loud.

​@NateNate  - just wanted to follow up and see if you were able to get an answer from this thread? If so please mark the best answer or if you figured it out post the answer then mark that one as the best answer.

While the answers contain good information, they were not able to solve the issue.

It appears Veeam does not support saving data that is stored “outside” of proxmox over iSCSI.
My fix was to go with a different solution from Veeam.  Setup a separate machine with Proxmox Backup Server running on it.

Thanks for the feedback!

Well, this is due to the fact that you are using RAW iSCSI disks with these VMs. Looking at the table on this page of the Proxmox documentation, this disk type does not support snapshots, but that’s a requirement for Veeam.

To work around this, you could e.g. use LVM on top of iSCSI.

Thanks for the info Matt!  This help!  I am curious if I can convert RAW disks to LVM after the fact?

Something i’ll look into. Your answer is marked as Best :)