Time Has Come for Another New System
The original Google storage file systems have served the company very well;
the company's overall performance proves this. But now, in 2009, the continued
stratospheric growth of Web, business and personal content and ever-increasing
demands to keep order on the Internet mean that Quinlan and his team have had
to come up with yet another super-file system.
Although Google folks will not officially sanction this information for general consumption, this overhaul of the Google File System apparently has been undergoing internal testing as part of the company's new Caffeine infrastructure announced earlier this month.
Google on Aug. 10 introduced a new "developer sandbox" for a faster, more accurate search engine and invited the public to test the product and provide feedback about the results. The sandbox site is here; as might be expected, there's also a new storage file system behind it.
"By far the biggest challenge is dealing with the reliability of the system. We're building on top of this really flaky hardware-people have high expectations when they store data at Google and with internal applications," Quinlan said.
"We are operating in a mode where failure is commonplace. The system has to be automated in terms of how to deal with that. We do checksumming up the wazoo to detect errors, and using replication to allow recovery."
Chunks of data, distributed throughout the vast Google system and subsystems, are replicated on different "chunkserver" racks, with triplication default and higher-speed replication relegated for hot spots in the system.
"Keeping three copies gives us reliability to allow us to survive our failure rates," Quinlan said.
Replication enables Google to use the full bandwidth of the cluster, reduces the window of vulnerability and spreads out the recovery load so as not to overburden portions of the system. Google uses the University of Connecticut's Reed-Solomon error correction software in its RAID 6 systems.