Proxmox VE 9 introduces external QCOW2 snapshots on thick-provisioned LVM volumes over SAN (including FC and iSCSI). There is already an updated plugin, that supports not only this version but also those specific snapshots.
Now, using a shared FC (or iSCSI) SAN is possible just like we did with VMware - while still being able to generate nice Veeam backups of the VMs on the LUNs: Plug-in for Proxmox VE v12.1.5.17 -> shared LVM? - R&D Forums
Here's the breakdown:
- QCOW2 is required for snapshot functionality on SAN LUNs.
- Snapshots are implemented as external overlays (not internal QCOW2 snapshots).
- Each snapshot creates a new logical volume to store delta data.
- This allows rollback and versioning, even on raw block devices like FC LUNs.
[TUTORIAL] - Inside Proxmox VE 9 SAN Snapshot Support | Proxmox Support Forum
⚠️ Limitations to Keep in Mind
- Performance impact: QCOW2 introduces overhead—up to 30–90% degradation compared to raw disks.
- Thick provisioning required: You must allocate full-size LVM volumes for both base and snapshot images.
- No linked clones: You can't create linked clones from templates using this method.
- Snapshot deletion can increase usage: Merging overlay data may defeat SAN thin provisioning.
- TPM support is limited: Snapshots of VMs using TPM are not supported.
- Not production-ready: This feature is currently a technology preview.
Let’s hope for the feature to become ready for production on the Proxmox side and also to get rid of the high performance impact it seems to suffer currently.