BigTable

BigTable is simplified structured data storage for large distributed system.
As opposite to google file system which is mainly for write-once read-many data, BigTable supports more frequent update. And this is especially engineered toward google's specific needs. For example, string is the only data supported.

This is google's answer to their persistant data storage needs, which is not supported by any existing databases. As system scales, there are many applications (or services) that traditional database system doesn't consider. Or, sometimes database system seems too general to be used for specific purpose. Trends are going backward, to build own storage system, at least for very-large services.