i had the same problem with two windows 2003 webservers.

I ran the Security Configuration Wizard on both servers and the wizard disabled the services "Microsoft Software Shadow Copy Provider" and "Volume Shadow Copy"

i set the startup of both services from "disabled" to "manual" and snapshots are working fine now.

also ensure that the "VMware Shadow Copy" service is set to manual startup

hope this helps

the error was constant, backup did never work.

I'm using the VMware Data Recovery Appliance for backup.

the Security Configuration Wizard is part of windows 2003 you can add/remove it through the windows components

but if you didn't use it your system was messed by something else.

If you do a manual snapshot via vsphere client be sure to uncheck "snapshot the virtual machine's memory" and check "quiesce guest file system(need vmware tools installed)

this also produces the same error a the backup appliance if the two mentioned services are disabled

We get the same error here on a few servers.

If I make some headway I will report, if someone else could do the same that would be great.

Cheers.

The VSS component is what is causing the problem you're facing, and there are a lot of different ways to workaround it, but the main thing you need to remember is that if you're not running VSS during your backup operations, you will not have an application or filesystem consistent backup, you will only have a crash consistent backup.

The main reason for VSS not working as expected is because the tools aren't installed properly, but sometimes it's just a matter of the VSS in Windows not being able to quiesce the filesystem because an application is demanding access from it, so it can't 'pause' the I/O within the VM (this commonly occurs in SQL/Exchange/Oracle/Citrix), or the VSS just isn't functioning correctly within the guest so when the VMware tools attempt to use the VSS to quiesce, it fails with an error that you can see in the Event logs.

The following KB's should help you diagnose the problem, and the first one -although the actual situation might not apply to you directly- the information within it will tell you how to disable the VSS/SYNC driver within the VM, the others help identify if the VSS is working within the guest (using ntbackup), and provide workarounds to known MS issues that prevent VSS from running correctly.  Remember also that you can only use SYNC or the VSS component, so when you're running the VMware tools installation, make sure you do it interactively so you can see which option is selected.

Unable to take a quiesced VMware snapshot of a virtual machine - http://kb.vmware.com/kb/1009073

Troubleshooting Volume Shadow Copy quiesce related issues - http://kb.vmware.com/kb/1007696

64bit Windows virtual machines generate errors when trying to use the VSS and NT backup - http://kb.vmware.com/kb/1003383

Here is a KB from Microsoft that explained the issue for me - http://support.microsoft.com/kb/904418

If the service " VMWARE Snapshot Provider" don't appear in the list of windows services, we have the same error (-3960).

It cause Snapshot with "Quiesce" option and backup with Data Recovery don't work.

In my case, I have followed the procedure of AlbertWT, and desinstall the WMWARE Tools.

I 've setup on automatic startup the service "Windows Management Instrumentation". Reboot. Install again the VMWare Tools.

The Service VMWARE Snapshot Provider is now present in the list of services, and start automatically.

The Backup w/ Datarecovery on this VM works perfect.

Any updates on this at all?  I have a similar situation, only I CAN take snapshots manually with no issues at all.  When I try to run vDR backups manually it fails immediately.

Here is the error message I get:  Failed to create snapshot for XXX-XX-WS, error -3960 ( cannot quiesce virtual machine)

6/3/2010 10:36:54 AM: Task incomplete

I am on ESXi 4.0 (update 1 patched to 256968) running View 4.01 on a 2008 R2 server that is not backing up.

Mike Forbes