Date - 06\2011
Affected Product & Version - NVBU 8.5.x
Affected Module & Version – Vmware Plugin
OS Version - N/A
Application Information - N/A
Error “Failed to fetch props for a VM: 4” when backing Fault Tolerant Enabled VM
When backing up fault tolerant Vmware Virtual Machines the job fails with the error: Error “Failed to fetch props for a VM: 4”
In vSphere 4 Vmware has introduced a new feature, the Fault Tolerance. Below is an explanation of FT from Vmware:
“VMware Fault Tolerance provides continuous availability for applications in the event of server failures, by creating a live shadow instance of a virtual machine that is in virtual lockstep with the primary instance. By allowing instantaneous failover between the two instances in the event of hardware failure, VMware Fault Tolerance eliminates even the smallest chance of data loss or disruption.”
Do not confuse this feature with the HA in vmware. FT (Fault Tolerance) is used in addition to HA. Please consult the Vmware Fault Tolerance white paper for more details.
Backing VMware Virtual Machine involves taking snapshot of the VM. This is not possible with FT enabled VM. Vmware does not support it as stated in the vSphere Availability Guide. Below is extract from the Vmware document:
“Snapshots. Snapshots must be removed or committed before Fault Tolerance can be enabled on a virtual machine. In addition, it is not possible to take snapshots of virtual machines on which Fault Tolerance is enabled.
VMware Consolidated Backup (VCB). You cannot back up an FT-enabled virtual machine using VCB, vStorage API for Data Protection, VMware Data Recovery or similar backup products that require the use of a virtual machine snapshot, as performed by ESX/ESXi. To back up a fault tolerant virtual machine in this manner, you must first disable FT, then re-enable FT after performing the backup. Storage array-based snapshots do not affect FT.”
There are different ways around this. One of them, as stated above, involves disabling FT before the backup.
Another workaround is to install a Netvault Client on the guest operating system and back it up like a normal client.