USB passthrough to OS X guest: why does hard disk not show in guest?

[alh2015]

We installed ESXi 6 on a Mac Pro (latest model) and are now trying to passthrough a USB hard disk to a OS X 10.10 Yosemite guest. The drive is connected to the host server, shows in vSphere Client and we can add it in the settings of the VM but it simply doesn't show in the guest OS. The drive is HFS+ formatted. Any idea on this (we tried EHCI, xHCI controllers etc.)?

Is the problem HFS+, the controller of the drive, or?

The same drive mounts fine in Fusion.

Any opinion on this highly appreciated.

[powellbc]

We are having his exact issue, though in ESXi 5.5. What is weird is the drive even shows up in the OS X System Profiler of the guest VM, but the drive never mounts.