You can add multiple USB devices, such as security dongles and mass storage devices, to a virtual machine that runs on an ESX/ESXi host to which the devices are physically attached. Knowledge of device components and their behavior, virtual machine requirements, feature support, and ways to avoid data loss can help make USB device passthrough from an ESX/ESXi host to a virtual machine successful.

When you attach a USB device to a physical host, the device is available only to virtual machines that run on that host. The device cannot connect to virtual machines that run on another host in the datacenter

A USB device is available to only one virtual machine at a time. When a device is connected to a powered-on virtual machine, it is not available to connect to other virtual machines that run on the host. When you remove the active connection of a USB device from a virtual machine, it becomes available to connect to other virtual machines that run on the host. host.

Connecting a USB passthrough device to a virtual machine that runs on the ESX/ESXi host to which the device is physically attached requires an arbitrator, a controller, and a physical USB device or device hub.

USB Arbitrator

Manages connection requests and routes USB device traffic. The arbitrator is installed and enabled by default on ESX/ESXi hosts. It scans the host for USB devices and manages device connection among virtual machines that runs on the host. It routes device traffic to the correct virtual machine instance for delivery to the guest operating system. The arbitrator monitors the USB device and prevents other virtual machines from using it until you release it from the virtual machine it is connected to.

If vCenter Server polling is delayed, a device that is connected to one virtual machine might appear as though it is available to add to another virtual machine. In such cases, the arbitrator prevents the second virtual machine from accessing the USB device.

USB Controller

The USB hardware chip that provides USB function to the USB ports that it manages. The virtual USB Controller is the software virtualization of the USB host controller function in the virtual machine.

USB controller hardware and modules that support USB 2.0 and USB 1.1 devices must exist on the host. Only one virtual USB controller is available to each virtual machine. The controller supports multiple USB 2.0 and USB 1.1 USB devices in the virtual computer. The controller must be present before you can add USB devices to the virtual machine.

The USB arbitrator can monitor a maximum of 15 USB controllers. Devices connected to controllers numbered 16 or greater are not available to the virtual machine.

USB Devices

You can add up to 20 USB devices to a virtual machine. This is the maximum number of devices supported for simultaneous connection to one virtual machine. The maximum number of USB devices supported on a single ESX/ESXi host for simultaneous connection to one or more virtual machines is also 20. VMware provides support for multiple USB devices.

For a list of supported USB devices for passthrough from an ESX/ESXi host to a virtual machine, see the VMware knowledge base article at http://kb.vmware.com/kb/1021345.