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Peripheral Virtualization over Ethernet

A post by Vladan Seget got me thinking about using virtual machines with various peripheral devices. Systems that require serial, parallel or USB connectivity are in many cases not virtualization candidates. System administrators can utilize a number of options to virtualize peripheral I/O.

For serial port connections, RS-232, RS-422 and RS-485 devices are by no means common but still are in place for line-of-business solutions that may interface to non-computer systems. A number of products are available for these applications. I have used both the Digi PortServer and the Comtrol DeviceMaster series of products. Both applications are similar in that the devices (serial ports) are extended to the Ethernet network via a special driver provided by Digi or Comtrol. They have management software so you can configure the ports to run in RS-232, RS-422 or RS-485 serial emulation mode. Various products support various levels of serial modes. Some are RS-232-only, while others will support all three modes.

For USB peripherals, the de facto product is the Digi Anywhere USB Ethernet USB hub. Like the serial port products, this device will extend USB ports to a server over the Ethernet network. Digi AnywhereUSB now also couples RS-232 serial ports on the same device as USB ports, which is a nice feature.

In both situations, using virtualized peripheral I/O comes with a couple of considerations. If the server (assuming Windows) was converted from a physical machine that had serial or USB ports, the virtual driver will install very easily. For a new-build virtual machine that has never had a USB or serial port installed, it takes a manual process to add the base serial or USB driver to Windows to enable the enhanced driver to work correctly.

It is important to note that virtualized peripheral I/O isn't going to be as fast as the directly attached alternative, so make sure the application in question can function correctly with these devices in use.

For parallel port applications, I'm not aware of any product that will extend a parallel port over the Ethernet network, though they may exist. I've had to provision USB and serial ports to virtual machines, but not yet a parallel port.

Have you ever had to utilize peripheral I/O for virtual machines? Share your comments here.

Posted by Rick Vanover on 05/13/2010 at 12:47 PM


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