I ran into an situation recently where a client needed a USB drive connected directly to an VMware ESXi 4.1 host. As many of you know, getting USB pass-through working is a challenge in of itself. There are lots of requirements to be met at both the host level and the guest VM level. The strange part was that I seemingly met all those requirements.
I had already added my USB bus controllers through Configuration –> Advanced Settings on the ESXi host. I had rebooted. Seemingly everything looked great and appeared as if it were passing-through. I confirmed my VM was running Hardware Version 7 and I added the USB Controller without incident. However, the USB devices was greyed out and when I selected it I received the following message.
There are no USB devices connected to the host.
Initially I had enabled all USB buses for pass-through. What I ultimately found was that by disabling the EHCI USB bus back in Configuration –> Advanced Settings, along with a another reboot, did the trick. The above message went away and USB devices were no longer greyed out. I was then able to add my USB drive to my VM without incident.
The challenge here is that by disabling EHCI you are ultimately disabling USB 2.0 support for your drive. You are backing yourself down to USB 1.1 and that means significantly lower transfer rates. It’s not ideal but in a pinch, where you have no other options, it may just be what you need.
The hardware in question was an HP ProLiant DL380 G7 and a Seagate external USB drive.
Hope this helps!