If the world moves toward "on demand" capacity and virtualisation, could you throw away all of your capacity planning tools? Although that may seem logical at first glance, the opposite may actually be true.

The move toward on-demand capacity is really an evolutionary process. Unless you are one of the few early adopters buying capacity on demand from service providers, you still have a limited amount of capacity. Yes, if you are virtualising resources, it may appear that you have more resources because you can shift them around to service the applications that need them most. But the fact of the matter is that you still have many applications vying for the same virtualised resources - so what happens when they all need the maximum amount of resources at the same time? You can't squeeze blood out of a turnip, and you can't squeeze more cycles out of over-committed servers.

That's why capacity planning is still necessary, despite the new technologies that can more fully utilise server resources by shifting them around as needed.

But the issues don't end there. In the past - or in the present, for some companies - the infrastructure remains relatively static unless you have major company initiatives going on. Capacity planning is much easier to do when the infrastructure is static. In some companies, capacity planning is done on a periodic basis, if it is done at all.

However, as companies start employing virtualisation technologies throughout their infrastructure, the infrastructure becomes much more dynamic as servers are provisioned and de-provisioned from server farms to adjust to varying application needs. So the shifts in the infrastructure create a "moving target" that makes it difficult to even figure out where things are, let alone understand the capacity of that newly shaped environment. This means the requirements for capacity planning tools have dramatically shifted from tools that were sufficient doing off-line planning to tools that are dynamic and adaptable to the new shifting environments.

Of course, for most companies, this is still looking ahead to the future - since most companies today are not extensively using virtualisation yet. But it doesn't hurt to understand what you'll need in the future as you purchase tools today. The cheapest tools are probably not the ones that will be of most value as the IT infrastructure begins to take on a more dynamic nature. No, I'm not necessarily advocating that you buy the be-all, end-all capacity planning tool that you'll need in the very distant future. But if you're buying a tool anyway, and it happens to have some features that will help you as you evolve to a better place, it may be worth it.

Don't make the mistake of turning a blind eye to capacity planning because of the promise of grid computing, utility computing, on-demand capacity, and more. It's my opinion that you may need capacity planning even more, rather than less, as we morph to these new paradigms.

Audrey Rasmussen is a vice president with industry analyst firm Enterprise Management Associates.