The Trade off between reliability and efficiency - by Peter Judge

Entities Mentioned

• Uptime Institute
• Peter Judge

1. 

   Sitting in the world of green data centres, it's easy to forget that many people look at data centres in an entirely different way. Before a data centre can be green, it has to be reliable.
   
   The move towards green data centres is about using less energy, and measuring that by showing a low PUE - the ratio of power used, to power delivered to the servers - or a low amount of power used per MIP of processing work. But most people buying data centre services are much more focussed on how reliable those services are, with fault-tolerance and uptime at a premium.
   
   Hearing of a new UK data centre - Computacenter's facility in Romford - I realised again that the two measures are often in opposition. Computacenter got a Tier IV reliaiblity grade from the Uptime Institute, and that requires it to have measures such as standby servers. These servers run in the background, doing no extra work, just waiting to pick up jobs in a a disaster. Not very green, really.
   
   However much of a head of steam green measures have got, we'd all have to admit that reliability measures like those from Uptime are way more established, so I asked the institute whether there is a conflict between reliability and efficiency, and which the users really want: "Sustainability and energy efficiency is fashionable, but reliability remains key to the data centre industry," said Uptime vice president Julian Kudritzki. "There are innovative and clever ways to get energy efficient solutions, but we have yet to see high availability clients make energy efficiency a priority."
   
   From Uptime's perspective, the media coverage of green data centers is out of proportion to the requirement from customers, but they can see the direction things are moving - hence there is a refinement of Uptime's four tier system of classification in the pipeline. The concept they are working on is "operational sustainability", which combines the two. The new scheme isn't due till May, and won't make a huge change to Uptime's classic four-tier scheme, but we can expect sub-classifications in each tier, from a to c, so a Tier III c data center will be world class in efficiency terms, as well as reliable, said Kudritzki.
   
   Data centers in Tiers I to III can all be made very efficient, he told me, but there is no way to avoid a step up to Tier IV, where the standby equipment naturally uses more power.
   
   I spoke to Philip Vandenberg of energy efficiency specialist Dimension 85, and he reckons that everyone's data centers are going to get more efficient - the current average is a PUE of around 2.2 but this is going to fall rapidly. Over time as the Tier system will become pervasive, understood and more widely adopted. PUEs will begin to align with the different tiers. Expect lower tiers to have lower PUEs from 1.2 upwards, with resilieince becoming a PUE premium and probably stabilising at about 1.8 for Tier IV."
   
   My prediction would be that users running services on more than one data center may be able to reduce their carbon footprint somewhat by migrating services between the two. Perhaps a company might be able to reduce its environmental impact by deciding that certain services (perhaps reporting) can tolerate a slightly less reliable service, where there might be small delays in the event of any failure. 
   

   
   

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