Problem Description
Virtual Machine backups fail during the snapshot creation phase. The Druva backup proxy attempts to trigger a VMware snapshot to quiesce the data, but the task fails immediately in vCenter with an "Incompatible device" error. This blocks the backup from initializing because the virtual disks cannot be frozen for processing.
Cause
The failure is caused by the presence of a SCSI Controller configured for Bus Sharing (either "Virtual" or "Physical") on the target virtual machine.
VMware vSphere does not support native snapshot operations for virtual machines that have SCSI bus sharing enabled. Because standard image-level backup solutions rely completely on VMware snapshots to create a consistent point-in-time copy of the virtual disks, the presence of a shared bus intentionally blocks the operation to prevent data corruption across clustered nodes.
Traceback
The following error will appear in the primary vCenter tasks or within the Druva Phoenix logs located at /var/log/Druva/EnterpriseWorkloads/vmware/backup:
[ERROR] SyncError: Incompatible device are present on VM.
[ERROR] Error <class 'pyVmomi.VmomiSupport.vim.fault.SnapshotIncompatibleDeviceInVm'>:
msg = "Virtual machine is configured to use a device that prevents the snapshot operation: Device '' is a SCSI controller engaged in bus-sharing."
fault = (vim.fault.SharedBusControllerNotSupported) {
msg = "Device '' is a SCSI controller engaged in bus-sharing."
}
Resolution
Choose one of the following methods depending on your infrastructure requirements:
Method 1: Disable Bus Sharing (If Not Required)
If the virtual machine does not act as a shared cluster node and the setting was enabled accidentally:
Power off the Virtual Machine.
Right-click the VM in the vSphere Client and select Edit Settings.
Locate and expand the relevant SCSI Controller (e.g., SCSI Controller 1).
Find the SCSI Bus Sharing drop-down menu and change the selection to None.
Click OK to save changes, power on the VM, and retry the backup.
Method 2: Exclude Shared Disks from Backup
If the VM is a cluster node and must retain bus sharing for specific multi-writer/shared data disks:
Ensure the primary OS disk (e.g.,
C:or/) resides on a standard SCSI controller with Bus Sharing set to None.Isolate all shared cluster disks onto a secondary dedicated SCSI controller (e.g., SCSI Controller 1) where Bus Sharing is kept enabled.
Edit your Druva Phoenix backup policy to exclude the specific disks attached to that shared controller.
Note: This allows Druva to successfully snapshot and protect the OS drive, though the shared data disks will not be protected via this image-level backup policy.
Method 3: Deploy an In-Guest Backup Agent
If the VM requires Bus Sharing for clustering and you must back up the data residing on those shared disks:
Image-level snapshot backups are fundamentally blocked by VMware.
To resolve this, install the Druva Hybrid Workloads FileServer Agent directly inside the Guest Operating System.
Configure a File-level or Volume-level backup policy within the OS. This bypasses vCenter completely and does not trigger a VMware-level snapshot.