Green data centres?

Posted November 26, 2007 at 7:47 pm by Bart van de Garde in Infrastructure.

CO2 reduction is a hot topic. You hear and read about it in the media every day. For a long time I wasn’t really into it, until last week when I watched the Inconvenient Truth and read the accompanying book.

I have to admit, I was deeply impressed by Al Gore’s account. After screwing in low-energy light bulbs and taking some other energy-saving measures, I kept on wondering whether it wasn’t possible to save to a much bigger extent somewhere else. When last week I walked through one of the data centres Jitscale uses, I noticed a lot of PDUs with energy consumption between 300 to 700 kilowatts. Maybe that doesn’t sound like all that much, but at home I use 3200 kWh per annum, so one PDU consumes as much energy in 4 to 10 hours than I do for my personal use in a whole year. When it comes to data centres, surely a lot could be gained, but can a data centre ever be truly green?

In the world of data centres, energy consumption has been a hot topic for years. Five years ago it was unimaginable a rack would use more than 8 Ampere (1840 Watts), today this would imply a nearly empty rack. The reason for this lies in several factors: the ever faster server CPUs, and making servers smaller. Today, a 1U chassis has the same amount of CPUs as a 4U machine used to have. As a rack takes more 1U servers than 4U servers, this means more CPUs, disks and memory per rack, so that adds up to considerably higher energy consumption per full rack.

The result of this development is that some data centres are no longer suitable for colocation of modern hardware. As most data centres (in the Netherlands) were built around 2000, they are designed for energy consumption per rack as was then considered standard. On this the required capacity for UPS, generators and cooling systems is determined. With modern hardware this means racks can only be filled partly and effective use of m2 decreases: so less racks per m2. The immediate consequence is that colocation costs per server have increased considerably in recent years. Space is no longer the key aspect of colocation, but energy consumption is.

With increasing hardware energy consumption the question arises when we’ll hit the ceiling. Fortunately, large manufacturers have now broken the tradition of equipping CPUs with an increasing clock speed to enhance speed. Reason for this includes the difficulty of cooling CPUs at very high clock speed and the usual decrease of “performance per watt”. With its AMD Opteron series, AMD has been leader for a long time but Intel has now caught up. In all benchmarks today you come, besides computing power, also across performance per watt, an energy sufficiency measure that shows the computing performance for each used watt of electricity. From a sustainable point of view a good development, because not only speed matters but also the amount of computer performance accomplished with a certain amount of energy.

In the end, more efficient processors are only a small step in reducing data centre energy consumption. In a normal situation the bulk of the systems only gets used for 20 to 30%. As for each system multiple active CPUs, disks, and memory banks are being used, this leads to a significantly lower performance per watt than with optimal use of systems. A good system utilisation rate is not only more efficient in terms of hardware depreciation costs but also has a big effect on total energy consumption of an environment. In recent years major steps have been taken in the IT sector to increase utilisation rates using virtualisation technology. Through his, the average system utilisation rate will be increased to around 80 to 90% per system, creating a much more efficient data centre. The underlying motivation is generally not of a green nature: by reduction of systems, hardware and colocation costs can immediately be saved, something that appeals more to most IT managers than sparing the environment. At Jitscale we are currently working on a project to reduce 2 racks fully filled with servers to only 2 physical servers in our virtualisation infrastructure. Besides reduction of colocation costs it helps to bring about all sorts of advantages regarding flexibility, availability and redundancy, and pay-per-use. A win-win situation, for both our clients and the environment.

This virtualization trend recently also takes hold of network equipment. Cisco started a campaign called “The Green Data Center”, focused on designing multiple functionalities and/or instances using virtualized solutions from a single hardware environment instead of installing a separate appliance for each function. This helps reduce the required hardware amount even more, and with that, the energy consumption. A great development that, besides reducing energy consumption, also offers more advantages. Jitscale won’t stay behind with these developments. This year we developed a new service where clients can purchase virtual firewalls, with a similar functionality to physical, dedicated firewalls but with a shared hardware platform.

The answer to my initial question is probably quite simple: data centres will never be truly green. With the ever increasing growth of internet and IT applications it is improbable this energy devouring industry will downsize, probably the contrary. Plus, applications are progressively more demanding in terms of CPU load (look for example at the shift from internet text to video content) making it highly unlikely the total data centre energy consumption will decline in the future. Within our sector a trend is set to choose more energy efficient hardware, usually motivated by cost savings and not by a green heart. With increasing social pressure on sustainable entrepreneurship, I believe it is a matter of time before data centres will need to compensate their energy consumption or will need to invest in (more) sustainable energy. While this undoubtedly brings higher costs, this will also serve as catalyst to design our data centres in a more energy efficient fashion, as recent years have already shown.