Why does a redis cluster require at least 6 nodes?

This is also a thought. You can create a redis cluster through redis-trib.rb, and then use the number after --replicas to indicate how many slave nodes correspond to one master node. , then I did the following test. (Recommended learning: Redis video tutorial)

The desired effect is to have 6 nodes, then 2 master nodes, and each master node corresponds to 2 slave nodes. Isn’t it exactly 6 nodes?, but an error is reported during execution:

[aiprd@hadoop2 src]$ ./redis-trib.rb create --replicas 2 192.168.30.10:7000 192.168.30.11:7003 192.168.30.10:7002 192.168.30.10:7001 192.168.30.11:7004 192.168.30.11:7005<br/>>>> Creating cluster<br/>*** ERROR: Invalid configuration for cluster creation.<br/>*** Redis Cluster requires at least 3 master nodes.<br/>*** This is not possible with 6 nodes and 2 replicas per node.  #解释了，对于6个节点，不可能是3个master，每个有2个副本节点。因为，那样的结构需要9个节点。<br/>*** At least 9 nodes are required.                              #至少需要9个节点。<br/>

The above information means: the Redis cluster requires at least 3 master nodes, so now There are a total of 6 nodes, and the only way is 1 master corresponding to 1 slave.

So:

1master-1slave, the redis cluster requires 6 nodes

1master-2slave, redis The cluster requires 9 nodes, and so on.

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