Cassandra is a distributed database management system designed for handling a high volume of structured data across commodity servers. It provides high availability with no single point of failure.
Apache Cassandra is an open source, distributed and decentralized/distributed storage system.
It is a column-oriented database.
Cassandra was developed at Facebook for inbox search.
FAULT TOLERANT:
Data is automatically replicated to multiple nodes for fault-tolerance. It supports replication across multiple data centers. This ensures the replacement of the failed nodes with no downtime.