FltGetVolumeGuidName returning wrong name?

This is a mini-filter on Windows 2003 SP2 x64.

When I call FltGetVolumeGuidName in my PreCreate (or PostCreate) callback, I get a valid-looking volume name. However, the GUID doesn’t match the actual volume GUID that I see from mountvol.exe. This only appears to happen on a shared volume on this server, while the local C: gets the proper volume GUID every time.

Unfortunately, this is a customer system, so debugging isn’t an option, though I have been able to run some tests to narrow it down to this.

The exact same binary works fine on every other system I’ve tried it on, even shared volumes on Windows 2003 clusters in my test setup.

Has anyone seen an issue like this before? Am I missing something obvious here? I suspect something specific to shared volumes on Windows 2003, but I’m not sure what might be going wrong or what I might possibly be doing wrong. Or if there’s some other way to get the volume GUID in the PreCreate callback.

Brian Groose