Cassandra is a relative latecomer in the distributed data-store war. It takes advantage of two proven and closely similar data-store mechanisms, namely Google BigTable, a distributed storage system for structured data, 2006 (http://static.googleusercontent.com/external_content/untrusted_dlcp/research.google.com/en//archive/bigtable-osdi06.pdf [2006]), and Amazon Dynamo, Amazon's highly available key-value store, 2007 (http://www.read.seas.harvard.edu/~kohler/class/cs239-w08/decandia07dynamo.pdf [2007]).
Like BigTable, it has tabular data presentation. It is not tabular in the strictest sense. It is rather a dictionary-like structure where each entry holds another sorted dictionary/map. This model is more powerful than the usual key-value store and it is named as column family. The properties such as Eventual Consistency and decentralization are taken from Dynamo.
We'll discuss column family in detail in a...