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What if every server in your virtualized data center was driving 10Gbps of traffic?

My team just completed a test with an end user where we drove nearly 10Gbps of traffic over Ethernet through a single Xeon 5500 based server running ESX4.0. The workload was secure FTP. Our results will be published in the next 30 days. We’ve seen 10Gbps through a server in several other cases (notably, video streaming and network security workloads) but this is first time we’ve really tried to do a 10GB “enterprise” workload in a virtualized environment. It took a fair amount of work to get the network and the solutions stack to work (we had to get a highly threaded open source SSH driver from the Pittsburgh Supercomputer Center, for example, to make it scale). We also found some good value for some of our specialized network virtualization technologies (i.e., the VT-c feature known as VMDQ). But, regardless, by working at it moderately diligently, we got it to work at 10Gbps and don’t see any real barriers to doing that in real production environments.

We also found that the solution throughput is not particularly CPU-bound, it’s “solution stack bound”. That means that workloads that are more “interesting” than virtualized secure FTP and video streaming are likely to be able to source and sync more than 10Gbps/server, too. And, when we get to converged fabrics like iSCSI and FCOE that put the storage traffic on the same network path (or at least the same medium) as the LAN traffic, we’d expect that the application needs for higher Ethernet throughput will increase.

So what? Well, if you buy the fact that virtualized servers can do interesting things and still drive 10GB/s of Ethernet traffic, you have to wonder what’s going to happen to the data center backbone network. If you have racks with 20 servers each, putting out a nominal 6Gbps of Ethernet traffic, each rack will have a flow of 120Gbps and a row of 10 racks will need to handle 1.2 Tbps. I’m not sure what backbone data center network architecture will be able to handle that kind of throughput. Fat tree architectures help especially if there are lots of flows between servers in close proximity to each other in the same data center. But, fat tree networks are very new and not widely deployed. Thoughts?

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