One of our customers uses VMware VCB backups integrated with CommVault Simpana. The CommVault job simply calls a pre-backup script to snapshot the VM and copy all the VM files to the VCB proxy, backs up the files from the proxy to the CommVault media server, then a post-backup script commits the snapshot and purges the VM files from the VCB proxy.
Recently, we upgraded this customer from VMware VI3.5 to VMware vSphere v4 Update 2. For most of the VMs that are backed up with VCB, we had no issues at all. The backups ran the weekend following the upgrade with no issues. However, all of the VMs that had been secured with the Windows Security Configuration Wizard would not back up. These VMs are in the DMZ and are locked down very tight because they host externally available web applications. The issue is that each time a backup was initiated from CommVault, the VCB script would return a non-zero error due to a snapshot failure in VMware. VMware’s error was “Cannot create a quiesced snapshot because the create snapshot operation exceeded the time limit for holding off I/O in the frozen virtual machine.” This would happen when using VCB scripts, but I could create a snapshot without error from the VI client. [more]
After much research and testing, I determined that the problem was hold-over from the VMTools upgrade. In the new version of VMTools, a new service is installed called VMware Snapshot Provider is installed. This service gets installed when VMTools is upgraded. Its purpose is to help facilitate application consistent snapshots through the VMTools. On the servers that were getting the “quiesced snapshot error”, this service was not present at all, but VMTools had already been updated…very strange. Here is where the Security Configuration Wizard comes in. Part of our lockdown policy is to disable a service called COM+ System Application. This service manages the configuration and tracking of COM+ based components. Apparently, without this service enabled, VMTools upgrade will NOT install the VMware Snapshot Provider service. Without the service, no quiesced snapshots and you get errors when creating snapshots via the VCB integration modules.
So why could I create a snapshot from the Vi client? Well, VMware knows that you are using VCB to create snapshots for the purpose of backup. What good would the backup be if it wasn’t app consistent? The VI client, on the other hand, will first try to create an app consistent snapshot, but if it fails or times out, it will go ahead and create the snapshot “crash consistent” without error. VCB is not as forgiving. If the guest quiesce fails, the snapshot fails…end of story. The solution was to uninstall the VMTools, reboot, temporarily enable and start the COM+ System Application service, install VMTools, then disable the COM+ System Application service. After I did that, backups have been running fine since.