I/O Bottlenecks Virtualization

By Andy Patrizio (Send Email)
Posted Dec 4, 2007


Xsigo Systems Monday released a study it says identifies a major complication in the deployment of virtualization servers: the data bottleneck from all of the I/O that takes place in a virtualized world.

A study from Xsigo Systems reveals the biggest hurdle virtualization faces may be the infrastructure it's supposed to be making more efficient.

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The current I/O infrastructure in servers was designed for traditional usage, which is typically one application or use per server. If a machine was acting as a Web server, it would connect to a database or e-commerce system, while a mail server would connect to a storage system.

This allowed for servers to run in a 1U "pizza box" style server with a single gigabit network connection. But in a virtualized system, multiple application servers require multiple connections and multiple Ethernet ports to handle several gigabits of data going in and out of the server.

To accommodate virtualization I/O, servers require six to 10 ports, which means a 4U box to handle all those cards and ports. The Xsigo survey found 75 percent of virtualized servers have seven or more I/O connections per server, compared to two to four connections for a server running without virtualization software.

So while virtualization may allow a data center to consolidate from 500 servers to 100 servers you end up with a spider web of cabling. "What ends up happening is you end up connecting everything to everything," Jon Toor, vice president of marketing at Xsigo told InternetNews.com. "People can overrun traditional I/O with services they have in a virtualized environment, unless you put a lot of the load in the same physical box."

Adding to the problem that ports are often assigned to applications by MAC address. It's difficult and time consuming to move an application to a new physical server because the networking has to be reconfigured on top of moving the application.

Xsigo found that 35 percent of virtualization users had to reconfigure I/O connections six or more times in the past year, usually when they moved a virtual server to new physical hardware.

The survey also found that 58 percent of virtualization users had to add connectivity to a server specifically for virtualization requirements, and because of this they had to use larger hardware, 4U instead of 1U, which consumes more power.

Xsigo Systems is a startup, launched in September specifically to address the I/O connection bottlenecks. Not surprisingly, its report suggests there's indeed a need for its products. Its flagship offering, the 780 I/O Director, provides a single interface into a 1U server for all virtualized connections.

Using one or two InfiniBand connections instead of multiple Ethernet connections, the Director can reduce the amount of cabling required by up to 70 percent, according to Toor, while providing a full 10-gigabit bandwidth for all virtual applications.

In a standard virtual server, each port runs at 1 gigabit and the ports are separated. With the Director, the full 10 gigabits are available to any application that needs it. So if one application requires several gigabits and the others don't require it, that app can have full access to all of the bandwidth.

Privately held Xsigo features some heavyweight venture backing from the likes of Kleiner Perkins, Khosla Ventures and Greylock Partners.

This article was originally published on InternetNews.com.

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