The so-called cluster is to provide the same service by adding the number of servers, so that the server can reach a stable and efficient state.
The necessity of using redis cluster
Question: We have already deployed redis , and can start a redis to read and write data. Why do we need to learn redis cluster?
Answer: (1) A single redis is unstable. When the redis service goes down, there is no service available. (Recommended learning: redis video tutorial )
(2) The reading and writing ability of a single Redis is limited.
Summary: The redis cluster is to enhance the reading and writing capabilities of redis.
redis master-slave replication
In the master-slave replication model, there are multiple redis nodes.
Among them, there is and is only one master node Master. There can be multiple slave nodes.
As long as the network connection is normal, the Master will always synchronize its data updates to the Slaves to maintain master-slave synchronization.
Features
(1) The master node Master can read and write.
（ 2) The slave node Slave is read-only. (read-only)
Therefore, the master-slave model can improve the reading ability and alleviate the writing ability to a certain extent. Because there is still only one master node that can write, all read operations can be transferred to the slave node, which improves the write capability in disguise.
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