Cassandra's data model offers the convenience of column indexes with the performance of log-structured updates, strong support for denormalization and materialized views, and powerful built-in caching.
Ceph is a distributed object, block, and file storage platform.
Couchbase Server is a high-performance NoSQL distributed database with a flexible data model. It scales on commodity hardware to support large data sets with a high number of concurrent reads and writes while maintaining low latency and strong consistency
Elasticsearch for Apache Hadoop (ES-Hadoop) is the two-way connector that solves a top wishlist item for any Hadoop user out there: real-time search.
MariaDB server is a community developed fork of MySQL server. Started by core members of the original MySQL team, MariaDB actively works with outside developers to deliver the most featureful, stable, and sanely licensed open SQL server in the industry.
An open-source distributed JSON document database with a pleasant and powerful query language.