Replication
Replication means that while you write to a Redis instance (usually referred to as the master), it will ensure that one or more instances (usually referred to as the slaves) become exact copies of the master.
Redis 2.8 introduced asynchronous replication, which makes slaves periodically acknowledge the amount of data to be processed. As you would expect, a master can have multiple slaves and slaves can also accept connections from other slaves.
There are three ways of making a Redis server instance a slave:
Add the directive slaveof IP PORT to the configuration file and start a Redis server using this configuration
Use the redis-server command-line option --slaveof IP PORT
Use the command SLAVEOF IP PORT
The following example starts three Redis instances: one master and two replicas.
On the first terminal, start the master redis-server on port 5555:
$ redis-server --port 5555
On the second terminal, start the first slave on port 6666:
$ redis-server --port 6666 --slaveof 127.0.0.1 5555...
