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Virtualisation - making the headlines
Posted in Infrastructure on 18 February 2009 by
It has been difficult to pick up an IT magazine recently and not find any number of stories on virtualisation. Whilst ‘virtualisation' seems a rather nebulous term that's easily adopted by vendors trying to spruce up their existing product line, its also true that it is starting to play a major role in infrastructure strategies - a trend that will only continue.
Anyone who has some interest in the virtualisation story will be familiar with VMWare; a company that has done more than anyone to push the topic up the corporate agenda. After an IPO last year, the company currently has a market cap of approximately £11 billion on an annual turnover of less than £1 billion - a clear indication that the market expects virtualization to be very big business in the coming years.
Whilst there are various types of virtualisation, VMWare focuses primarily on ‘server virtualisation' with its VMWare Infrastructure ESX product suite. Server virtualisation exploits the fact that continual performance increases in server hardware mean that in many instances a server runs at only a fraction of its full capacity - a bit like a high performance car which is only used for city shopping. And whereas its obviously possible to put additional applications on a lightly loaded server, IT departments are often wary of doing this because they fear that a problem with one application will spill over and impact everything else running on the server. With virtualisation, applications are truly isolated because each virtual server runs its own copy of the operating system.
So with server virtualisation, you can make more efficient use of your server hardware, potentially reduce the number of servers that you need and so save energy, cooling and rack space costs into the bargain. Clearly this is a tempting proposition, but if these were virtualisation's only advantages, I doubt there would be quite such a level of interest as we're currently seeing.
Intriguingly, the real benefits of server virtualisation occur when companies move away from having individual disk drives in each server and move to a shared storage model by using a SAN. This is because a virtualised server consists of only a small number of files, with the operating system, applications and middleware encapsulated within a set of image files. Anyone familiar with imaging as a technique for accelerating the deployment of desktop machines will know that an image is usually intrinsically connected with the particular hardware set of the machine that was used to produce the image. However, with server virtualisation, the virtualisation layer makes all hardware appear consistent - which makes it possible to run the virtualised server images on ANY compatible hardware platform - not just the specific hardware used to build the image.
With the virtual server images held on shared storage, it's possible to quickly move a virtual server from one physical server to another. In VMWare, "quickly" means practically real-time, and even whilst the server is functioning - which means that if a physical server suffers a hardware failure, its workload can be quickly redistributed across other physical servers in the resource pool without the users being any the wiser. This ability provides the potential for a radical approach to High Availability and Disaster Recovery, and one that is understandably a mouth-watering prospect for anyone responsible for designing and operating a server infrastructure.
What makes server virtualisation even more compelling is that the options for implementing shared storage are getting greater, and costs are coming down. iSCSI, which allows SAN to be accessed across standard Gigabit Ethernet cards and switches provides a significantly cheaper alternative than Fiber Channel, and despite some limitations can work very well in many circumstances. Equally, when speed of performance isn't critical, there's the option to use cheaper SATA disks in pace of SAS disks which might be 3-4 times the price for the same capacity. Put these things together, and a SAN becomes a viable option for all but the most modest of infrastructures.
Adrian Polley, CEO, Plan-Net
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