After twitter, now is Digg who decided to replace MySQL and most of their infrastructure components and move away from LAMP to another architecture called NoSQL that is based in Casandra, an opensource project that develops a highly scalable second-generation distributed database. Cassandra was open sourced by Facebook in 2008 and is licencied under Apache Licenses..
The reason of this move as explained by John Quinn in digg blog is that their primary motivation for moving away from MySQL was the increasing difficulty of building a high performance, write intensive, application on a data set that is growing quickly, with no end in sight. This growth has forced them into horizontal and vertical partitioning strategies that have eliminated most of the value of a relational database, while still incurring all the overhead.
Cassandra is a distributed database with a BigTable data model running on a Dynamo like infrastructure. It is column-oriented and allows for the storage of relatively structured data. It has a fully decentralized model; every node is identical and there is no single point of failure. It’s also extremely fault tolerant; data is replicated to multiple nodes and across data centers. Cassandra is also very elastic; read and write throughput increase linearly as new machines are added.
Casandra is in use at Rackspace, Digg, Facebook, Twitter, Cisco, Mahalo, Ooyala, and more companies that have large, active data sets. The largest production cluster has over 100 TB of data in over 150 machines.
Untill now, no reaction has been signaled from Oracle the actual owner of MySQL database, because this big move of Digg and before twitter will make other big companies follow the same way in the future and leave MySQL for NoSQL.
SP: Anyway, aside from MySQL and NoSQL, we also have SQL to think about which works best with windows web hosting.
Usefull Links : http://www.digg.com;