nodetool drain 

Drains the node.

Drains the node.

Synopsis 

$ nodetool <options> drain
Options
Short Long Description
-h --host Hostname or IP address.
-p --port Port number.
-pwf --password-file Password file path.
-pw --password Password.
-u --username Remote JMX agent username.
-- Separates an option from an argument that could be mistaken for a option.

Description 

Flushes all memtables from the node to SSTables on disk. Cassandra stops listening for connections from the client and other nodes. You need to restart Cassandra after running nodetool drain. You typically use this command before upgrading a node to a new version of Cassandra. To simply flush memtables to disk, use nodetool flush.