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So why virtualise? Because everyone else seems to be doing it? I hope not! Most server systems are under-utilised; general estimates say that an average Windows server is running at around 15% utilisation and UNIX environments at about 20-30%. That’s pretty low. In order to gain a more personal analysis, I ran a small audit of six servers. All run Linux and host various high-demand services such as mail serving, mail routing/scanning, file serving, web services and database hosting. The results were interesting.
Two servers showed intense usage–one server had constant usage of 90-98% (may be time to upgrade this one) and the other fluctuated with the norm being 10% but regular peaks of 65% were observed. A third server showed an average usage of 10% with irregular peaks to 20% utilisation; the remaining three systems were showing very low utilisation of 0-5%. These last four servers could be good candidates for virtualisation. Why? Well, with combined peak utilisation of 35% and an average figure of just 20% they can happily run on one physical platform without encountering performance problems.
Other than increased utilisation of resources, what benefits would be gained migrating from these four systems on to one physical server.
Saving physical space is the most obvious answer. As a rule, our server rooms don't grow along in sync with demands from the business. Unless the entire company is considering an office move, IT departments will have to work within their given space despite increases in demand. It is obvious that replacing four 2U servers with one more powerful 2U server is going to free up 6Us of space, although this is optimistic, and realistically 4Us would be freed (I'll explain the grounds for this later), this is still a huge saving in real estate and will enable twice the number of services to be hosted in the same physical space. Many firms turning to virtualisation will look at moving to blade servers at the same time to maximise space savings.
Reduced hardware costs are another advantage of virtualisation. In the example of my four under-utilised systems, all could be migrated to one server of the same specifications and still have adequate resources, that's at 25% of the current hardware cost. Even if I were to over-spec the new system to allow for future increases in usage, the savings are not to be ignored.
Reduced power consumption and need for cooling are benefits which come hand in hand. While the power consumption and heat output of a system with high levels of utilisation will be greater than that of a system under a lesser load, the consolidation of multiple low-load systems should still produce less heat and demand less power over all. Data centres are finding it increasingly more difficult to keep up with demand for power at the rack and the cooling demand which comes with increased power consumption (and that additional cooling also requires power, increasing overall running costs).
The ability to rapidly deploy a new system without ordering new hardware, building/installing the server, and updating firmware can be a big time saver for sys admins (whose time is usually at a premium).
Although the above does not give an in-depth explanation of the many advantages afforded by virtualisation, I hope it gives an informative overview of benefits when compared to the more traditional server farm model. There is an abundance of information to be found on both TechRepublic and Google and this briefing should give those interested in the topic a starting point for further research. I was hoping to also discuss the potential weaknesses of virtualised services and the conceivable actions which can help to neutralise these risks (and in some cases make virtualisation a more solid and lower-cost approach) however, I seem to have run short of time so will look at this next week rather than hastily fumbling over the subject now.
Ref: http://blogs.techrepublic.com.com/networking/?p=134
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