Cassandra's design is premised on the points outlined in the Dynamo: Amazon's Highly Available Key-value Store paper (https://www.allthingsdistributed.com/files/amazon-dynamo-sosp2007.pdf). Specifically, when you have large networks of interconnected hardware, something is always in a state of failure. In reality, every piece of hardware being in a healthy state is the exception, rather than the rule. Therefore, it is important that a data storage system is able to deal with (and account for) issues such as network or disk failure.
Depending on the Replication Factor (RF) and required consistency level, a Cassandra cluster is capable of sustaining operations with one or two nodes in a failure state. For example, let's assume ...
