Tapping into a network of satellites orbiting the Earth, a GPS receiver can pinpoint your location, but it can also tell time. Rather than rely on outside clocks, Google equips its Spannerized data centers with its own atomic clocks and GPS (global positioning system) receivers, not unlike the one in your iPhone. "It's a time reference that's owned by Google." "We wanted something that we were confident in," Fikes says. It's a time reference that's owned by Google.'īut with Spanner, Google discarded the NTP in favor of its own time-keeping mechanism. >'We wanted something that we were confident in. In July, several big-name web operations experienced problems - including Reddit, Gawker, and Mozilla - because their software wasn't prepared to handle a "leap second" that was added to the world's atomic clocks. But because it takes time to move information across a network, this method is never completely accurate, and sometimes, it breaks altogether. This is essentially an online service that connects machines to the official atomic clocks that keep time for organizations across the world. Typically, data-center operators keep their servers in sync using what's called the Network Time Protocol, or NTP. The team includes not only Fikes and Hsieh, who oversaw the development of BigTable, Google's seminal NoSQL database, but also legendary Googlers Jeff Dean and Sanjay Ghemawat and a long list of other engineers who worked on such groundbreaking data-center platforms as Megastore and Dremel. They have a history of doing the unexpected. The assumption was that consistency was barred by the inherent delays that come when sending information between data centers.īut in building a database that was both global and consistent, Google's Spanner engineers did something completely unexpected. Yes, we had "NoSQL" databases capable of storing information across multiple data centers, but they couldn't do so while keeping that information "consistent" - meaning that someone looking at the data on one side of the world sees the same thing as someone on the other side. But as the web grows, its creations so often trickle down to the rest of the world.īefore Spanner was revealed, many didn't even think it was possible.
Google's web operation is significantly more complex than most, and it's forced to build custom software that's well beyond the scope of most online outfits. "It's definitely interesting," says Raghu Murthy, one of the chief engineers working on the massive software platform that underpins Facebook - though he adds that Facebook has yet to explore the possibility of actually building something similar.
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