Two 300-megahertz (MHz) Dual Pentium II servers with 512 megabytes (MB) of memory
A four-processor F50 IBM RS6000 computer with 512 MB of memory
A dual-processor Sun Ultra II computer with 256 MB of memory
Several hard drives (some of which were housed in a box covered in LEGO bricks) ranging from 4 to 9 gigabytes (GB) for a total of more than 350 GB of storage space [source: Google Stanford Hardware]
Today, Google uses hundreds of thousands of servers to provide services to its users. Google's strategy is to use relatively inexpensive machines running on a customized operating system based on Linux. A program called Google File System manages the data on Google's servers [source: Google Cluster Architecture].
Google uses servers for different tasks. Web servers receive and process user queries, sending the request on to the next appropriate server. Index servers store Google's indexes and search results. Document servers to store search summaries, user information, gmail and Google Docs files. Ad servers store the advertisements Google displays on search pages.
Google divides the information on each index server into 64 MB blocks. There are three copies of each block of data, and each copy is stored on a different server running on a separate power strip. The blocks of data are distributed semi-randomly so that no two servers have the exact same collection of data blocks. That way, if there's a problem with one server, the data will still exist in other machines. Using multiple copies of data to prevent an interruption in service is called redundancy.
A master computer manages each set of servers. The master computer's job is to keep track of which servers hold each block of data in the event of a catastrophe. If one server goes down, the master computer redirects all traffic to the other servers containing the same data.
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