Google is reportedly experimenting with the open source version of Sun's Solaris operating system as a possible long-term prelude to replacing its massive global network of Linux servers.

With dozens of data centres worldwide housing hundreds of thousands of Intel servers supporting its flagship search engine, a Google move to OpenSolaris would be another of several recent votes of confidence for the platform.

Google officials have, as ever, declined to comment. But according to Sun and other sources, a number of other companies are using Solaris 10 or Solaris Express, the executable version of OpenSolaris. That list includes eBay, Yahoo, Vonage, Wal-Mart, Disney and Reuters.

"Google, eBay, Yahoo - pick your favorite," said Sun CIO Robert Worrall. Worrall said that Google already runs a "significant amount" of Solaris in its data centres and is one of a number of customers "excited about the possibility" of moving more Linux servers to AMD Opteron servers from Sun running some version of Solaris.

Google runs a stripped-down version of Red Hat Linux specially modified by its engineers. But another source, a Solaris systems administrator who recently interviewed for a job at Google, said he was told the company plans to create and test its own modified version of OpenSolaris.

"I am 100 percent certain that there are literally dozens of people horsing around with OpenSolaris inside Google," said Stephen Arnold, a technology consultant and author of The Google Legacy. Moving to OpenSolaris, he said, would be a natural move for Google, with its large number of former Sun employees. But Arnold said he doubts that Google is deploying OpenSolaris widely yet. "Will it quickly replace Linux anytime soon? No," he said.

Propelled by the release of Solaris' source code 15 months ago, as well as new AMD-based servers from Sun that run it, the old operating system is experiencing something of a mid-life resurgence. More than five million users have registered to use Solaris 10 since its release in January 2005.