John Thompson: Virtual Instruments was created in 2008 as a private-equity-led carve-out from Finisar, the networking-components maker. I joined in 2010 as CEO, thinking it would be a part-time job until we found a permanent leader. It’s been a full-time job.

What is the business and why the split from Finisar?

Virtual Instruments monitors the routing of information between servers and storage to make sure the whole data center is healthy. We can tell you where the performance and utilization problems are for all your networks. Finisar sold technology to other technology companies. It did not have the DNA of selling to big businesses, which is what we do.

So you’re saying IT departments need simpler products, just like those for consumers?

That’s exactly right. They don’t want to spend weeks or months or years to understand your product in order to get value from it.

Who are your customers?

We have a little over 300 clients now. They tend to be among the largest users of technology, especially companies with equipment in their data centers from multiple providers as well as multiple software applications. They include PayPal, Wells Fargo, and Apple. We also help companies size their data centers correctly. AIG is using us to help go from 32 global data centers to two.

Was it a challenge to go to a smaller company?

A career is all about following your passion. Bigness is ego talking. It’s better to let your intellect talk. For my next gig, I’m going to have an idea with a friend, and we’re going to get a barn.

Looking back on your IBM experience, how important is corporate culture?

As a company grows, its management systems must change to accommodate a bigger and different company, and its culture must change as well. IBM required a leader, Lou Gerstner, to say, “This is what we’ll do and not do, and here is the behavior that will be rewarded and punished.” Over time that changed IBM’s corporate culture. You don’t change a corporate culture overnight.

Will Satya Nadella, Microsoft’s new CEO, need to change the company’s culture?

That’s a better question for Satya, but there are some attributes of Microsoft today that look like IBM circa 1990. For example, the Windows monopoly is under attack. To deal with that, Microsoft will have to change many things.

Connected is an interview series with leaders of innovative organizations. Conversations are condensed and edited. For more Q&A and video, go to fortune.com/connected.

This story is from the March 17, 2014 issue of Fortune.