Cassandra solves this problem by simply removing the master instance from the picture. In Cassandra, when a piece of data is written, the write is sent to all of the nodes that should hold a copy of that data; no single node is authoritative. This neatly solves the availability problem: with no master instance, there is no single point of failure. If a node becomes unavailable, the data intended for it is still written to the other nodes that should store it; the application need not halt the writing of the data.
In fact, Cassandra is even more robust when a node is unavailable to receive a write. Through a process called hinted handoff, other nodes in the cluster will store information about the write request ...
