How green is my V-word?
Does virtualisation = energy savings?
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No, not "valley" as in John Ford's 1941 classic movie based on Richard Llewellyn's 1939 best-seller about a close-knit, hard-working Welsh coal-mining family at the turn of the twentieth century. Nor "vampires" as in the somewhat less classic episode from the Masters of Horror TV series that introduced the "V-word" concept. It's not even the euphemism increasingly being used to avoid saying "Vietnam" when analysing current events in Iraq.
No, we are referring to that current IT hero, Mr Virtualisation and, in particular, to his pairing with that latest industry poster-child, Ms Green Computing. Is this a celebrity couple to match the Beckhams now they have left for the sunnier climes of LA?
Here is the basic premise; virtualisation means consolidation and increased utilisation, and hence less servers. Fewer servers mean less power, which in turn means less CO2, thus saving the planet. Simple.
Or is it? I have heard it said: "Yes, you have fewer servers in a virtualised environment, but each one of those servers is more heavily utilised. Because they are doing more work their power consumption goes up. What you gain on the swings you lose on the roundabouts. The net gain is zero."
Who is right? Let's look at it in more detail. Say you virtualised and consolidated four identical servers that are 20 per cent utilised, into one physical server. That server is now 80 per cent utilised. Making the somewhat simplistic assumption that power usage ramps linearly with utilisation means power consumption will also increase from 20 per cent of the maximum possible to 80 per cent. But the processors are not the biggest users of the power drawn by a server - according to IBM only 30 per cent gets used by the processors. The other 70 per cent is used-up by the power-supply, fans, disks, memory, etc.
So the increase from 20 per cent to 80 per cent actually represents 60 per cent of a slice that is only 30 per cent of the overall pie; the total server power draw increases by 18 per cent. In return for this modest increase you have removed three complete servers from the data centre, and overall power consumption has gone down from four "original server units" to 1.18, a pretty hefty 70 per cent saving.
Of course, this is somewhat simplistic. The fans and the power supplies will have to work a bit harder because of the extra power drawn by the processors, but it still represents a significant saving when compared to what you will get from any new power saving hardware features. Power consumption improvements in the processor, disks, power supply, and cooling areas tend to be incremental. When added together they do become more significant, but are still not anything like the step change you may expect to see from virtualisation.
Virtualisation is not a panacea for all power and cooling problems. For a start not all servers virtualise well, especially those with I/O-intensive workloads like database servers. And with 65 per cent of the power coming into a typical data centre going on stuff other than the IT workload (such as air conditioning), power savings at the server may not be directly reflected in the overall data centre electricity bill. Unless your cooling system is sophisticated enough you may just end-up blowing cold air over the three quarters of floor-space that are now empty.
So what is the lesson? Establishing exactly what power savings you are going to get from an infrastructure virtualisation project is not straightforward (hence the title), but virtualisation will almost certainly be the most important step you take in this area. It seems slightly ironic that a software solution (virtualisation) may play the largest part in solving what is essentially a hardware problem.
You will not only be saving the planet, but also money. With the total power costs over the lifetime of a server currently estimated as being in the region of 50 per cent of the hardware costs, self-interest may play as big a part here as enlightened altruism. And you get to feel good about yourselves at the same time, never mind the PR mileage. It is not often that an economic force (greed) coincides with the common good (or at least looking good). When they do, watch out for an unstoppable bandwagon. Better still, jump aboard.
Copyright © 2007, Quocirca
COMMENTS
That Vauxhall advert...
...makes me laugh.
They say they've cut the carbon footprint at their Ellesmere Port plant by 30%
Could this be because they're making 30% less stuff there these days?
http://news.bbc.co.uk/1/hi/wales/north_east/4994814.stm
As someone famous once said, there's lies, damn lies and green statistics...
pointless?
I think there has been some great input in all the above but have to say the article/heading/topic does seem a little misguided.
It does seem a bit like asking if a paintbrush is artistic or not! ... i.e. virtualisation is an fantastic enabler for change, this doesn't mean it is green in itself, nor does it mean anyone who uses it will automatically gain environmental impact advantage.
I do wonder if this was deliberate just to park the reactions?
Production engergy costs
I work at a company which builds electronic devices and I find it plausible that the production of a computer takes way more energy than it's operation.
Just look at a typical motherboard. Every little part is packaged in a lot of plastic which gets thrown away. The soldering process takes quite a lot of energy and many boards need to through it several times.
So what you need to minimize is the amount of new hardware buildt.
BTW, power supplies tend to be more efficient when evenly loaded. If you can guarante a certain amount of load, you can even use some with a far higher efficiency than typical computer PSUs.
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