Although GFS provides Google with reliable, scalable distributed file storage, it does not provide any facility for structuring the data contained in the files beyond a hierarchical directory structure and meaningful file names. It’s well known that more expressive solutions are required for large data sets. Google’s terabytes upon terabytes of data that they retrieve from web crawlers, amongst many other sources, need organising, so that client applications can quickly perform lookups and updates at a finer granularity than the file level.
So they built BigTable, wrote it up, and published it in OSDI 2006. The paper is here, and my walkthrough follows.