We have a USB hard drive dock connected to our physical server that we use for nightly backups from virtual machines. Last week I noticed that even though I had swapped to a different hard drive, it still registered the old one, and our backup had failed. I checked the cables, removed the usb device from the virtual machine and tried to add it back. Vsphere said the operation had been successful, but the device never showed up on the VM. I tried adding a different USB hard drive, with the same result. I tried different usb ports, I tried different VMs, I tried rebooting the VMs, rebooting the main server, and restarting the management agents, with no luck. Any ideas?