Google has a patent for a "Leasing scheme for data-modifying operations". If we look closely at the abstract, we'll notice that the patent refers to Google File System (PDF), "a scalable distributed file system for large distributed data-intensive applications".
"A system may facilitate performance of a data-modifying operation in a file network that includes multiple servers that store replicas of data. One of the servers may serve as a primary replica for one of the replicas of data and at least one other one of the servers may serve as at least one secondary replica for the replica of data. The system may send data associated with the data-modifying operation to the primary replica and the at least one secondary replica based on a network topology and independently send a data-modifying control signal that requests execution of the data-modifying operation using the data associated with the data-modifying operation to the primary replica and the at least one secondary replica."
The file system deals with error detection, fault tolerance, automatic recovery and files that have more than 1GB. This is one of the most important assets of Google and this is responsable for you not losing your mails when a disk failure happens in one of the machines that store your documents.
{ Via Search Engine Watch. }
