It seems that you can hardly read anything online about data centers without reading about the wonders of virtualization. Virtualization involves condensing multiple physical machines down to one physical machine running multiple virtual machines in software. This saves power, physical space, and cooling. The problem is, the hype misses what should be the first consideration.
By example, consider two seperate physical servers, each running Unix/Linux, one server running as a web server, the second server running as a mail server. Replacing these two servers would require a server with adequate capacity to run both applications and three instances of the operating system software (the base server and two virtual servers). While this is certainly legitimate to do, the first thought should be to CONDENSE services, not virtualize.
Condensing services requires consideration of why the services were split between multiple servers in the first place. Were the original servers not powerful enough to run both services? This is eliminated by the larger server required regardless of whether you choose to condense or go virtual.
Were the original services seperated so that a single hardware failure would not effect both? In this case, neither condensing or virtualizing would be appropriate, since both services would end up running on the same physical machine, removing the hardware redundancy.
Condensing the services directly onto a single physical server has the benefit of increased efficiency (only one copy of the operating system is running), provides easier administration (one machine to administer rather than three), and reduces complexity.
Are there valid scenarios for virtualization? One case would be where the services require different operating systems to run. Another would be where seperate administration is required (ie virtual private servers sold to multiple individuals). Condensing can even be combined with virtualization! The end goal is maximum efficiency gain from the investment in new hardware and the effort involved in converting.
Virtualize for all the obvious benefits but consider condensing services first for
the best results!
Vern Burke, SwiftWater Telecom