IT technologies—especially virtualization technologies—are still evolving. This can be evidenced in the number of hypervisors that are being brought to market in quick succession. Interestingly, all of them are offered free of charge and all of them have their unique architectural approach, creating excitement and confusion in the minds of end- users.

Amidst the marketing noise, you may even hear the statement that the choice of hypervisor is irrelevant and that is why it is given for free.  Is that true? Since they seem to be free, do all of them serve the same purpose, and deliver the same value–zilch?  The answer is no. The architecture of the hypervisor makes all the difference in performance. Mature architectures obviously deliver greater value to the user than those that are still evolving. The efficiency of the hypervisor is determined by the way in which it makes use of the supporting hardware. The bottom line is that customers must get the real picture before they get carried away by all the hype.

What are the real factors that must be considered while evaluating hypervisors?  VM density is the first factor that has to be evaluated.  IT managers need to evaluate VM server infrastructure using the time tested cost per application methodology. This will help them understand the costs of the different components—Hypervisor efficiency and Virtual infrastructure management efficiency. Hypervisor efficiency will be determined by the number of hypervisors that will be required to support a given number of Virtual machines running an application. Virtual infrastructure management efficiency will be determined by the extent of management software required to manage the hypervisor environment. These two elements will determine the total cost of acquisition such as licensing of operating systems or acquisition of physical servers.

But, the very important part of the evaluation is the VM density. How many VMs can be effectively consolidated on the hypervisor without creating performance loss?  The more the number of VMs that can be loaded the greater will be the cost savings. Since operating system licensing and hypervisor instances are interconnected, the number of hypervisor instances that need to be used will dramatically impact costs.

It follows that not all hypervisors are equal even when they are free. The hypervisor density needs to be tested if you want to get a good bargain.