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• Blade Servers and the Density Dilemma

  September 11th, 2008 : Rich Miller

  Are blade servers the answer? That depends upon the question, and some data center operators should be asking more questions before looking to blades, according to Microsoft’s James Hamilton. High-density blade server installations can create as many problems as they solve, James argues in a thorough examination of server density on his Perspectives blog.

  Hamilton points out that filling racks with blade servers can result in rack power loads of 25kW and beyond, which usually leads to liquid cooling solutions – which may not have been factored into the original cost/benefit analysis for the blade servers. It’s an informative look at power, space, cooling and PUE in evaluating the cost of optimizing your data center.

  “I’m not saying that there aren’t good reason to buy high density server designs,” Hamilton writes. “I’ve seen many. What I’m arguing is that many folks that purchase blades, don’t need them. The arguments explaining the higher value often don’t stand scrutiny. Many experience cooling problems after purchasing blade racks. … In short, many data center purchases don’t really get the ‘work done per dollar’ scrutiny that they should get.”

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A Ramirez

Posted September 12th, 2008

Look at the power efficiency per blade compared to regular rackmount servers. You will find that blades are up to 40% more efficienct in power terms. When you are deploying 1000+ servers in a datacenter, this rapidly becomes a compelling argument.

The “blades are too dense” argument is not sensible. Put less blade chassis per rack if you cannot handle the density. Even at one chassis per rack (say 4-5kW), you are still deploying a very significant compute resource, and most likely getting more compute than you would otherwise deploy in the entire rack.

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