Google is moving to Debian Linux for the computers supporting it's Cloud storage servers. Previously, the stripped down Linux OS GCEL (Google Compute Engine Linux) was used for this. Debian is a well-established Linux distribution, and forms the basis for Ubuntu and other distros.
TheRegisterDebian is a famously stable Linux distribution. Version 7 was released earlier this week after over two years of development. "If you're looking for a stable, rock solid Linux distro the new Debian will not disappoint," wrote our own penguin fiddler in a review of the distro.