Datacentre Algebra

Posted by Karen on Jan 28, 2013 12:00:00 AM
If, like the vast majority of the population, you’ve never set foot inside a datacentre, then they may well be a bit of a mystery to you – large, nondescript buildings hosting the mystical cloud.

Of course you may have seen some photos of the interior of a facility, but if you have, in magazines like Wired or the Economist, then it’s probable you’ve glimpsed at the facilities of Google or Facebook and witnessed a glossy, shiny premises with row upon row of nicely colour coded servers, routers and switches all working 24/7.

Datacentres for major corporations like Google (who have seemingly limitless budgets) are one thing, but how do the “real” businesses find data centre space and what should they be looking for?

This article has not been written to hark on about the cloud and its benefits; that subject has been exhausted almost as much as the word ‘cloud’ has been printed in marketing campaigns. But rather to begin to break through the marketing jargon and be a useful guide to understanding what sort of data centre would be right for your business.

For many of us, irrespective of our technical qualifications, reading a datacentre specification sheet can be a most confusing exercise. In fact in many ways it almost seems as if you are studying maths; the sheets are riddled with algebraic equations and terminology such as 2N power redundancy, with N+1 cooling with VESDA Gas Suppression units delivering FM200…

Working on a recent project at our newest colocation facility in Manchester, Joule House, I’ve managed to gain some understanding of the algebra and with it what businesses should be looking for in a facility.

To begin with it’s important to understand that both power and cooling are delivered using generators and refrigerators; essential to keeping your equipment working 24/7. The total number of generators or refrigerators needed is called “N”. N is the optimum number but has no resiliency, so if a generator were to fail you would lose power. Therefore what many facilities do is introduce an extra fully redundant generator; this is referred to as N+1. If the total number of generators required (N) is 1 then you have 100% redundancy. However if you require three generators then you have a 33.33% redundancy.

The next very familiar equation is N+2. This follows the same principle and delivers two additional generators or refrigerators. If N=1 then you have 200% resiliency, if N=4 you have 50% resiliency. What I am hoping to show here is that because of how datacentres report resiliency an N+1 facility might be very different to another. However, as we spec up the resiliency we get to 2N. This is the first time where you can be sure of resiliency - as 2N means that the facility has 2xN or double the number of generators and refrigerators needed to operate. Therefore regardless of whether the facility operates 2 generators or 200 they have confirmed that they have double the capacity.

So what should I look for?

    - Your data centre should be a custom built facility with demonstrable security.

    - Your data centre should be away from water and have risk assessments proving they are not at any flood risk (as New York proved).

    - You should be asking if the facility is “Carrier Neutral”. Some datacentres are operated by a single carrier who then monopolise the connectivity. This may cause you issues if you take services from other providers or wish to create a mirrored datacentre setup in the future for further resiliency.

    - Geography: Most colocation hardware is created to be manageable offsite; therefore geography should not be a major concern. In the event of a reboot being needed or a cable needing to be run you should be able to use the remote hands facility. Therefore understand the remote hands procedure and do not allow geography to limit your choice.

    - Touring and Security: Your datacentre will hold the most sensitive parts of your organisational data; this may be your CRM or billing platform. Therefore when you tour the facility (which I strongly recommend you do) be mindful of the security, did they do thorough security checks? Are the suites secure? Who has access to your racks? If you are not satisfied with the security this is not the facility for you.

    - Restrictions: It is important to understand what the limitations of the datacentre are. Many datacentres will have strict cabling and rack policies, these are not necessarily bad as they ensure security and continuity allow for faster time to repair and reduces the chance of accidental cable damage. You have the most flexibility before the racks are installed so do your capacity planning thoroughly and talk about your three to five year plans. Future racks may be located in a completely different section of the building so understand what impact this would have.

    - Advice. Always ask for advice and use the pre-sales resources on offer.

      I hope this proves useful to those wishing to understand more about datacentres and in particular to anyone confused by DC terminology.
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