Converged Network Savings Less Than Expected

Posted by Howard Marks
February 09, 2010

The proponents of converged data center networks, especially those in the FCoE camp, take it as an article of faith that their new network architecture will be less expensive than separate data and storage networks. When I sat down to figure out the real cost of connecting a server to the data center network, I was surprised that my FCoE configuration was just $300/server, or 5 percent, cheaper than using separate 10Gb Ethernet and 8Gbps Fibre Channel networks.  

Knowing zealots on both sides would want to poke holes in my assumptions, let alone my calculations, I've posted my Excel Spreadsheet (FCoE cost.xlsx) so you can take a look and come to your own conclusions. I also included the more common scenario of six 1GbE data connections plus FC for storage traffic, which is the most expensive alternative, almost 15 percent more than the FCoE config.  

The biggest take away from this little thought experiment is that we should all now be using 10GbE in the data center. It's cheaper than multiple 1Gbps connections without even figuring in the extra cost for additional cable management hardware and the headache of the spaghetti bowl in the back of your racks.

I based my calculations on the cost of a new rack with twenty 1 or 2u servers, as I expect most user organizations will make the transition to new data center networks on a rack-by-rack basis.  Twenty servers works out just right for a pair of 24-port switches at the top of rack with four ports left for uplinks. The GbE example uses four 48 port switches with 10Gb uplinks, and so would need additional ports on the core network, further boosting the cost of that solution.

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