IOmeter doesn't see Storage Spaces vdisks

I've created vdisks (Storage Spaces- one simple and one parity) in Server 2012R2 and they show up in Server Manager, but IOmeter (2006.07.27) doesn't show them-  only the physical disks show up.  However, if I create a volume (and file  system) on the vdisk, then it shows up in IOmeter- but I've never had to do that before, and I've used IOmeter quite a bit.  Is there something that needs to be done?  Thanks.