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The Meaning of “Scalable” Needs to Change

The word “scalable” has been used in IT for over forty years. IBM used the word when they first talked about their 360 series of mainframe computers in the 1960’s. Since that time scalability has been a consideration in every aspect of computing: mainframes, minis, personal computers, servers, networks, proprietary systems, open systems, even smartphones.

But up until recently, “scalable” usually meant that you could make a system scale up — you could add more computing power and run the same application with much higher transaction volumes. That’s what most people were interested in: being able to reuse their application architecture for higher volumes as their companies grew.

We began to see the need for downward scalability about twenty years ago during the beginning of the outsourcing era. As IT organizations outsourced some of their applications, they needed less processing power on the computers they had been using for those applications. But they found that it wasn’t very economical to scale down. Vendors usually offer you great deals to trade-in your smaller hardware for bigger boxes, but you won’t find such a good deal when you want to replace a large box with a smaller one.

In the last ten years, virtualization has had a large impact on scalability. With virtualization you can carve up a large computer into a series of smaller virtual computers, then alter the size of those virtual computers at will.  Virtual computers can scale both up and down, but you’re still stuck with the large computer that’s underneath all of those virtual systems.  So while virtualization can help you balance computing load across your different systems, it doesn’t help much if your overall enterprise computing requirement is shrinking.

More recently, “cloud computing” has given us an outsourced version of virtualization. Now our virtual computers can exist at a vendor location or even at a combination of onsite and remote facilities.   Scalability has gotten many times more flexible, with its limits determined more by what we can negotiate than by the limits of physical computer hardware.

Yet despite all of the advances that have been made in virtualization and cloud computing, I still hear the word “scalability” primarily referring to the ability to scale up. It’s like our IT people have been trapped in the scale-up definition for so long that they forget that downward scalability is important too.

Take a look at IT departments that are doing well in the current bad economy. You’ll find that in many cases their success is due to their ability to provide the same systems capabilities at much lower volumes with corresponding reduction in cost. Downward scalability is helping them be successful in a time when revenue and system volumes are declining.

So when you look at a new application system as a candidate for use in your company, make sure that it’s scalable both upward and downward. Your success — and the success of your company — may depend on it.

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  • Harwell July 8, 2009, 3:56 pm

    I should also mention that downward scalability is not only important for applications, hardware and networks. It’s also important for service contracts, including contracts with software vendors for licenses. An ideal contract not only defines what happens if your volume or license count goes up — it also defines how your total price goes down if your volume or license count declines. This can make a big difference in your costs during a time of economic hardship. Be sure that your contracts allow for downward scalability as well as upward scalability.

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