A Bird? A Plane? No, a Virtual Switch

Arthur Cole

By this time, just about everybody knows that virtualization does wonders for your server farm, but places enormous new burdens on network and storage infrastructures.

Networking, in particular, is under a lot of stress as it has to contend with 10, maybe 12, servers where once there was just one. Even 10 GbE architectures are starting to hit the wall, which is why systems conforming to the new 40 G and 100 G Ethernet standards are so highly anticipated.

However, virtualization has a habit of solving some of the problems it helps create. A perfect example is the virtual switch, a layer of data management that can be integrated into the hypervisor that helps shuttle packets from virtual resources through physical network connections much more efficiently. They become increasingly important as virtualization expands beyond the server and into the desktop.

Citrix is the latest to add virtual switch capability, adding it to the new XenServer 5.6, along with a number of related technologies like self-service VM administration and a new IntelliCache system for VDI deployments. Citrix based its design on the Open Virtual Switch format, featuring a bridge technology that allows it to communicate with all current network bridges and adapters without having to adjust frame formats or other parameters. It also includes forwarding and filtering technology designed to help enterprises manage and maintain QoS levels. And with hardware acceleration on the adapter from companies like Solarflare, throughput can be doubled or even tripled in the virtual network.

Many of the leading network hardware platforms come with their own forms of virtual switching as well. Cisco's Nexus 1000V plants a virtual switch inside the VMware ESX server where it runs versions of the NX-OS operating system. The system is used primarily to run VM traffic as well as mobile security and network policy applications. The company packages the system along with its Unified Compute System architecture to help enterprises manage data loads across virtual infrastructure and out on the cloud.

Not everyone is a fan of the virtual switch, however. Extreme Network's James Owens wonders why, in an age of flattened, fabric-based networking, would anyone want to add yet another tier to their environment? He says a much more efficient approach is to place all VM switching on the network, as is done on the company's Direct Attach architecture. Not only does this provide wire-speed throughput, but it provides visibility into inter-VM traffic. By doing the same thing for blade servers, the company says it can reduce current five-tier networks down to two by eliminating the blade and top-of-rack switch layers along with the virtual switch. He adds that the DA architecture uses no proprietary technology and doesn't require a forklift upgrade.

So is the virtual switch a worthwhile investment, or just a technology detour? There's a lot of money riding on the fact that it is the answer to heavy virtual traffic. But it's also true that network simplicity is a laudable goal in the drive to reduce costs and cut carbon emissions.

It's almost certain, though, that the network you use today won't be the same creature by mid-decade.

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