Economics of Virtualization May Be "Off Planet"
by Mark Ontkush, Boston, Massachusetts, USA on 07.20.07
With the promise of reduced costs and increased efficiency, the virtualization rage continues in the techno-sphere. The basic premise of virtualization is to make one server do the work of many; this increases utilization, and hence requires less servers. Fewer servers mean less power, which in turn means less CO2, thus saving the planet. Simple.
But now there's a counterpoint; "yes, you have fewer servers in a virtualized environment, but each one of those servers is more heavily utilized, and because they are doing more work their power consumption goes up. The net gain is zero." Can that be? When we interviewed Foedus, they claimed one could get up to a 20 to 1 reduction in hardware using virtualization; it's hard to believe that doesn't more than make up for the extra power. Quocirca did their own analysis and came to the same conclusion. On the other hand, when we interviewed John Engates of Rackspace, he agreed that the power to run the heavier-laden box beats the costs of buying it - the juice beats the iron.
There's got to be missing pieces of the puzzle here - perhaps not all servers virtualize well, or we need to take into account the specific kinds of applications being served. And other items, such as ambient temperature and facility design, clearly make a big difference as well. The takeaway is that, like most things, establishing what power savings you are going to get from an infrastructure virtualisation project is not straightforward, but there is a potential for a win-win here - you will not only be saving the planet, but also money. And 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; this TH is still for jumping on the calliope.::Quorica :: The Register
So what if a smaller number of machines individually use more power than under-utilized systems? Never mind the dollar figures - what about the environmental cost of mining the raw materials, refining the steel and silicon, creating the PCB boards (and eventually throwing them in a landfill where they can leach toxins into the groundwater), shipping the servers to the data centers, and the power/freon for the cooling systems? Virtualization IS GREEN.
Virtualization's benefits are rather tricky to determine. For instance, replacing 4 1U Dell PowerEdge 1435's (each with a 600W power supply) with 1 4U Dell PowerEdge 6850 (with dual 1475W power supplies) would appear to require more power. But you could run all 4 of the PE1435's OS's as a virtual machine on the PE6850, and still have room to add more. Let's assume that a 20:1 reduction is quite exceptional, and a 10:1 ratio is more realistic. 10 PE1435's that are now running on 1 PE6850 would result in 6000W of power being reduced to 2950W, a significant savings.
You can also think about materials usage as virtualization begins to become more mainstream. 1 4U server will certainly require less components than 10 1U servers, so buying habits will help contribute to virtualization's benefits.
Lots of servers are actually heavily utilized and you can't replace those with virtual servers. I.e., If you actually need twenty servers to serve your website replacing them with one box and twenty virtual servers is going to be impossible.
While some companies have a separate box for a print server, mail server, accounting server, etc, etc, many others do not. Maybe this will be sort of a win in the corporate windows world, but I don't think it will really affect the majority of servers racked up in datacenters around the world.
Virtualization is Green, but it is also very hyped as a solution to everything when it is really a solution to a specific issue.
We do see a large drop in our electricity consumption when migrating from multiple non-virtualised to virtualised servers. Virtualisation is a solution to more than one problem!
Too sagefool1975: Yes many servers are running at high utilization rates but they are often running on old Iron or not necessarily the optimum architecture. The other thing to look at is if you have application which peak at different times of the day.
I personally moved eight 2u application/web servers running at 60% - 80% utilization to two 1u servers and the new servers are running at under 20% utilization at peak! I moved from Sun's Ultra Spark IIIi chip to the Ultra Sparc T1. It's only one generation difference but the T1 is designed for the application I'm running and does a great job of it.
When thinking about the benefits of virtualization, it's important to think about the shape of the power vs. computation curve: It's not linear. Having a computer power supply plugged in while the computer is in complete stand-by mode can consume about 40W. A computer turned on and idle could consume 80, etc. Taking the CPU up to full load might consume only another 30-40W. Virtualization saves that baseline power draw where it costs a very large amount of power to just have a computer on and waiting for a job to come along. Of course, virtualization only works in cases when the servers being virtualized aren't 100% busy, but bursty workloads are very common in all kinds of computing applications. There are lots of very real scenarios where virtualization can provide a big reduction both in power and in the number of computers required to handle the aggregate workload of a bunch of services. But as with most things, "it depends on your workload."
Virtualization does more than save power, it saves materials as well, can reduce or eliminate the need for data center expansion (building materials and building footprint, gone), and decouples application additions from physical ones, as many conversations when adding a given app used to start with, "we need to get a box to do this", and went from there.
On the other hand it would be nice if programmers were environmentally aware. Very few think about power consumption, yet their decisions can mean that a disk stays spinning all night or not, or that a CPU works 10 times as hard to do the same thing. Energy efficiency is similar to performance (but not always), and performance is an old goal. However, with today's fast hardware performance is not the priority it used to be.
Is anybody talking about Green Software Practices? Somebody should be.
The company I work for vitualised over 700 servers last year. We did it to save rack space , cut hardware purchase costs and reduce the number of physical servers that we need to continue to maintain.
For this company saving power is not a key driver for virtualisation but is a nice bonus if we can get it.