eCos real-time OS makes short work of building a SAN appliance

Compellent has been shipping its SAN appliances to small to medium-sized companies for three years, growing from $4 million in annual sales to more than $23 million last year. Part of the reason for that growth, says cofounder John Guider, is that Compellent executives have recognized the value of making an open source operating system one of the building blocks of the company’s SAN offerings.

Compellent’s SAN appliance, called Storage Center, works from a GUI console that manages servers in any location using a “wizard-based” interface. Storage Center automates most of the tasks that network managers typically have perform manually, most notably the task of “tiering,” or deciding where in the SAN to store certain classes of information to create the most efficient system of data storage possible. Most of the time, data is classified according to the frequency of access, with data that is expected to be accessed less frequently stored on lower performance, less expensive drives, and more frequently accessed information stored on high performance disks. The Storage Center automates this task by placing metadata identifiers on each block of information that tell the software things like when the data was last accessed.

Guider says there was no point in starting from scratch when it came to choosing what architecture should undergird Compellent’s automated tiering capabilities. “Any smart developer knows that you want to use something already available. The operating system was the first thing we had to deal with in implementing the software.” Guider knew he wanted to use an OS with real-time capabilities to power the SAN appliance, so it could write, access, retrieve, and deliver data quickly across the network.

Guider was drawn to eCos, an open source real-time operating system, because of its highly configurable nature. He calls it an “application-specific” OS, and believes that because developers can tweak it to their apps, it delivers faster run-time performance. The fact that it is open source made it a great choice for budgetary reasons and what Guider calls “schedule savings,” because his development team didn’t have to call on a vendor to perform needed customizations.

Instead they pulled the source code, made the necessary changes to the kernel, added some driver support, “and had it up and running in a couple of weeks,” says John Veit, Compellent software engineer. Veit didn’t hit any snags with the software or with the development community surrounding eCos. Compellent had lined up distribution channels before it even began shipping its products, creating a built-in audience for the development process. “Some customers were not believing that we could have done this in the time we have done it,” Veit says. “A good part of it is due to the fact that we used the open source OS.”

Guider and Veit looked at other OS options, including VxWorks and QNX, but their colleagues recommended eCos for its stability and flexibility. “It’s not just cost,” Guider says. “I always think of engineers as a limited resource. With eCos, we used the engineers in a more productive way. This is code that has been out in the field for a long time in a variety of applications, and it is very solid. It’s a very valuable thing to have. The engineers are much more focused and we are able to have a much more robust product.”

Guider says his customer never question the fact that there’s an open source operating system underlying the SAN appliance. “We really don’t advertise what the operating system is. Sometimes people ask, but there’s never been a negative response.”