Just a few years ago, Thomas M. Siebel often faced skepticism when encouraging big companies to adopt internet-style cloud computing. Many companies, he said, had qualms about relying on the faraway data centers.

Now his customers have a different concern: One cloud service isn’t enough.

“They don’t want to be tied to one big tech company,” said Mr. Siebel, chief executive of C3 IoT, a software company that uses cloud computing to analyze data coming from industrial machines.

And Mr. Siebel is adapting. After initially working closely with Amazon, a pioneer in cloud computing, C3 IoT now also has a technology and marketing partnership with Microsoft. And it is negotiating a similar agreement with Google.

For a few years, it looked like Amazon would run away with the cloud computing business, piling up market share as it has with online shopping. But in the past couple of years, many companies have decided that they don’t want to depend on Amazon alone, and are spreading out their business.