Many organizations have saved both time and money by converting underutilized physical servers into virtual machines and consolidating those machines onto fewer physical servers. IT folks are understandably proud of what they've done at that point. But if you stop there, you might be leaving money on the table. There can be plenty of additional savings to be had by consolidating virtual machines, hosting multiple applications on some of your virtual machine instances.
I recently spoke with Ron Potter, TeamQuest's Manager of Best Practices. Ron says there are two common avenues organizations can follow to exploit virtualization. The first is one primarily motivated by cost and environmental savings. The second is one of dynamic routing of transactions and images to provide massively scalable operating environments. If your motivator is primarily cost savings and you aren't pursuing the massively scalable environments using tools such as VMware DRS, then Ron is a proponent for consolidating virtual machine instances, i.e. running more than one app per virtual machine.
Virtual machines need administrators too. Whatever your virtual machine-to-sys admin ratio is, eliminating some of those machines will save you some admin time. That's time that would otherwise be spent monitoring, maintaining, securing, backing up, and tuning all of those virtual machines. The fewer machine instances you have to manage, whether they are virtual or physical, the less admin time and effort will be required.
Reducing the number of virtual machine instances usually reduces operating system overhead, which will in turn cut demand for physical hardware requirements. Reducing hardware infrastructure will help trim space, power and cooling requirements too.
Ron says not to forget about software license costs. Depending on the OS you are running, you'll have to pay for each instance, not to mention the inevitable middleware and management software that is required for each virtual machine instance. Depending on the terms of your application software license agreements, there can be big savings there as well. Generally speaking, running software on fewer operating system images will simplify and reduce license costs.
If you have the performance tools necessary to properly plan and monitor your virtualized environment, there's no technical reason you can't begin a wave of virtual consolidation after your initial P2V wave of consolidation. You might, however, run into some politics. Your virtualization vendor has likely sold folks on the idea that there should be just one app per virtual machine. You'll need a plan that can convince everyone that running more than one will still perform while saving money.
You might also see resistance from business units unwilling to share a virtual machine instance with apps from other business units. That issue is probably best settled by working with management. You might need some new chargeback functionality to keep everyone happy.
Create a plan with goals and metrics for success, such as the number of servers decommissioned, software license reductions, or overall cost savings. Make note of service level requirements coming from the customers, departments or business units you are serving.
Basically our best practices manager is saying that a lot of the same techniques you used to consolidate physical-to-virtual will work virtual-to-virtual. And you'll get similar results: savings in hardware, software, space, power, cooling, and system administration requirements.
Ron's ideas sound like common sense to me, and yet they run contrary to the advice that you may have heard from other vendors. I think it's because Ron is seeing it more from the point of view of a business manager rather than as a vendor of virtualization technology.
For more detail, be sure to check out Ron's white paper on this subject, and by all means, add your comments and observations to this blog entry.