Redis clear understanding of the master + replica + sentinel and a standard cluster

Question

I came across multiple things:

1. Redis cluster with multiple master and their corresponding replica(s).
2. Redis master + replicas with sentinels.

As per https://redis.io/topics/cluster-tutorial a replica could be promoted to be the next master in case the original master fails. If this is so, why is the Sentinel process needed?

I need clarification on the cluster, cluster with Sentinel.

Are replicas and slaves absolutely the same in the context of Redis?

Answer 1

Redis Sentinel is used for standalone deployed Redis instances.

Redis Cluster does failover by nodes in the cluster. It does not need the help of Redis Sentinel.

In a word, you don't need Redis Sentinel when deploying Redis Cluster.