Windows Failover Cluster - Shared Volume twice in Backup

[mdiver]

We are backing up a quite large Windows File Server Failover cluster with two nodes.
They share a quorum drive and a 30TB data disk in a shared VMDK on FC inside VMware. This is a supported scenario according to VMware and Microsoft.
We are backing up this two node cluster using VAW in failover cluster mode via the shared AD object.

I would expect the shared 30TB volume to appear in the backup only once - no matter which node owns the disk currently - as VAW is aware of this disk sharing.
But we find VBKs for the weekly fulls of 60TB in size that implies the shared disk to be in the backup twice.

We opened a support case already (#7966451), but support only suggested to enable and optimize deduplication using larger (?) block sizes.
From my understanding we should not need any dedup. The disk should be in the backup only once in the first place.
Or did I get something wrong?

Thanks,
Mike

[Mildur]

Hi Mike

Yes, it should be protected only once.
Did you have a chance to check the question I asked yesterday regarding this topic?

In the past, when a job was unsuccessful, a full backup of all shared disks was initiated. This issue should generally be resolved now, except for a few edge cases.
Did you notice any errors in the job? Were the jobs retries?

Best,
Fabian

[mdiver]

No failures - at least in most recent full. Also no retries in latest run. There were some before, as the repo got full (because of data doubling).
Maybe support could check what's really inside the VBK?