diff --git a/plugins/hypervisors/vmware/src/main/java/com/cloud/hypervisor/vmware/resource/VmwareResource.java b/plugins/hypervisors/vmware/src/main/java/com/cloud/hypervisor/vmware/resource/VmwareResource.java
index 56d08a4e088e..c168277eaaf5 100644
--- a/plugins/hypervisors/vmware/src/main/java/com/cloud/hypervisor/vmware/resource/VmwareResource.java
+++ b/plugins/hypervisors/vmware/src/main/java/com/cloud/hypervisor/vmware/resource/VmwareResource.java
@@ -7239,7 +7239,9 @@ private List<UnmanagedInstanceTO.Disk> getUnmanageInstanceDisks(VirtualMachineMO
                                     instanceDisk.setController(DiskControllerType.getType(device.getClass().getSimpleName()).toString());
                                     instanceDisk.setControllerUnit(((VirtualSCSIController) device).getBusNumber());
                                 } else {
-                                    instanceDisk.setController(DiskControllerType.none.toString());
+                                    String msg = String.format("Controller of disk %s is unsupported", instanceDisk.getLabel());
+                                    s_logger.error(msg);
+                                    throw new Exception(msg);
                                 }
                                 break;
                             }
@@ -7264,6 +7266,7 @@ private List<UnmanagedInstanceTO.Disk> getUnmanageInstanceDisks(VirtualMachineMO
                         instanceDisks.add(instanceDisk);
                     }
                 } catch (Exception e) {
+                    instanceDisks.clear();
                     s_logger.info("Unable to retrieve unmanaged instance disk info. " + e.getMessage());
                 }
             }
@@ -7274,9 +7277,7 @@ public int compare(final UnmanagedInstanceTO.Disk disk1, final UnmanagedInstance
                 }
 
                 int extractInt(UnmanagedInstanceTO.Disk disk) {
-                    String num = disk.getLabel().replaceAll("\\D", "");
-                    // return 0 if no digits found
-                    return num.isEmpty() ? 0 : Integer.parseInt(num);
+                    return disk.getPosition() + (disk.getControllerUnit() * 100);
                 }
             });
         }