Several days ago, Lori MacVittie posted at DevCentral on the problems with Cloud Math:

It’s been a long time since I had the (mis)fortune to sit in a math class, so bear with me while I figure this out. In order to determine my daily budget for the application I am hosting with Google’s App  Engine, I need to sum the results of the standard deviation of the derivative of yesterday’s CPU utilization, multiplied by the bandwidth used divided by pi and then multiple the whole thing by the number of e-mail messages sent by the application. Got that? Go.

It’s the quintessential problem with cloud computing in relationship to the enterprise. In days like these, reducing costs associated with anything, particularly infrastructure, is considered a Good Thing.

In general, though, we’re not trained to think in these terms, which is why we see cloud computing implementations limited generally to web services and Web 2.0 applications.

This, of course, leaves out the largest segment of the computer using population, the workplace.

Capacity planning has always been more art than science, but there has been science in it, at least, and didn’t require a PhD in calculus.

One of the hardest things to wrap your head around will be the fact that it’s nearly impossible to determine what the concurrent user and request capacity of your application may be based on those free thresholds because, well, you probably haven’t been able to load test it.

Google and other cloud providers can – and most do – offer up statistics on resource use (how else could the bill/track/manage those variables if they didn’t have them available), but they’re usually based on application, not necessarily per request or per user so capacity planning at this granularity may require some heavy math and good guestimates. So what is the maximum amount you’re willing to pay on a daily basis given those parameters? And how much goes where? What if you don’t allocate enough storage and over provision the CPU? Or vice-versa?

Feels like, if you ask me, bidding on e-Bay. It’s a gamble, calculated to be sure, but a gamble nonetheless.

You can read more here, but I can speak to what’s personally kept me from recommending cloud solutions to clients and using them personally in the past: for existing sites and services, figuring out exactly what this is going to cost is difficult. It’s easier to go with a provider of standard hosting solutions I’m familiar with.

For those of us who have Rain Man-ish capabilities for mental calculation, there’s cloud computing migration.  For the rest of us, do we just suck it up or do we ask our providers for better ways to estimate our costs?