At a recent conference for application programmers, EclipseCon, Urs Hoelzle, a vice president of engineering and of operations at the search giant, shed some light on how Google's data centres operate. Many people consider the company's operations expertise more valuable than the actual search algorithms that launched the enterprise.
The way Google has been able to build out its computing infrastructure for millions, rather than tens of millions, of dollars is by buying relatively cheap machines. Looking at hardware costs, company engineers saw that purchasing a few high-end servers, with eight or more powerful processors, costs significantly more than dozens of simpler "commodity" servers.
The trick is to make these racks of hardware operate in tandem and to ensure that the failure of one machine does not derail an operation, such as returning a search query or serving up an ad.
Urs Hoelzle
VP of operations
and of engineering,
Google
Consider a home PC, Hoelzle said. Optimistically, a consumer PC might crash once in three years from a software glitch or hardware problem.
"At Google scale...if you have thousands of PCs, you can expect one (failure) a day," he said. "So you better deal with that in an automated way, or you will have service outages."
Google, known for its rigorous hiring practices aimed at attracting the brightest minds in computer science, has created a number of software tools to handle its computing installation.
The company wrote its own file system, called Google File System, which is optimised for handling large, 64 megabyte blocks of data. Significantly, the file system was designed to assume that a failure, such as a failed disk or unplugged network cable, can happen at any time.
Data is replicated in three places, and there is a "master" machine that can locate copies of a piece of data, such as a keyword index, if the original is out of commission.
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