6.0.1

You can add multiple devices to a virtual machine, but only one at a time. The virtual machine retains its
connection to the device while in S1 standby. USB device connections are preserved when you migrate
virtual machines to another host in the datacenter.
A USB device is available to only one powered-on virtual machine at a time. When a virtual machine
connects to a device, that device is no longer available to other virtual machines or to the client computer.
When you disconnect the device from the virtual machine or shut the virtual machine down, the device
returns to the client computer and becomes available to other virtual machines that the client computer
manages.
For example, when you connect a USB mass storage device to a virtual machine, it is removed from the
client computer and does not appear as a drive with a removable device. When you disconnect the device
from the virtual machine, it reconnects to the client computer's operating system and is listed as a removable
device.
USB 3.0 Device Limitations
USB 3.0 devices have the following requirements and limitations:
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The virtual machine that you connect the USB 3.0 device to must be configured with an xHCI controller
and have a Windows 8 or later, Windows Server 2012 and later, or a Linux guest operating system with
a 2.6.35 or later kernel.
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USB 3.0 devices are available only for passthrough from a client computer to a virtual machine. They
are not available for passthrough from an ESXi host to a virtual machine.
Avoiding Data Loss
Before you connect a device to a virtual machine, make sure the device is not in use on the client computer.
If the vSphere Web Client disconnects from the vCenter Server or host, or if you restart or shut down the
client computer, the device connection breaks. It is best to have a dedicated client computer for USB device
use or to reserve USB devices connected to a client computer for short-term use, such as updating software
or adding patches to virtual machines. To maintain USB device connections to a virtual machine for an
extended time, use USB passthrough from an ESXi host to the virtual machine.
Connecting USB Devices to a Client Computer
You can connect and chain any multiple low, full, and high- or super-speed USB hubs and devices to a client
computer. Careful planning and knowledge of hub behavior and limitations can help ensure that your
devices work optimally.
USB physical bus topology defines how USB devices connect to the client computer. Support for USB device
passthrough to a virtual machine is available if the physical bus topology of the device on the client
computer does not exceed tier seven. The first tier is the USB host controller and root hub. The last tier is the
target USB device. You can cascade up to five tiers of external or internal hubs between the root hub and the
target USB device. An internal USB hub attached to the root hub or built into a compound device counts as
one tier.
The quality of the physical cables, hubs, devices, and power conditions can affect USB device performance.
To ensure the best results, keep the client computer USB bus topology as simple as possible for the target
USB device, and use caution when you deploy new hubs and cables into the topology. The following
conditions can affect USB behavior:
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Connecting or chaining multiple external USB hubs increases device enumeration and response time,
which can make the power support to the connected USB devices uncertain.
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Chaining hubs together increases the chance of port and hub error, which can cause the device to lose
connection to a virtual machine.
Chapter 6 Configuring Virtual Machine Hardware
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