We have a 3 node redis cluster with redis and sentinel running on all three nodes. One of the node is master and other two are replicas.
There are some situations when one node goes down and in those cases one of the replica nodes is promoted to master without any issue.
Now we have a use case when two nodes goes down and we want last remaining node to be promoted to master. we dont want quorum to set 1 as this may lead to some unnecessary failovers. Please suggest the possible solutions.
Assuming you run both Sentinel and Redis processes on each one of the 3 nodes, your deployment can handle a failure of single node only. This is because after two nodes goes down, there is only one running Sentinel process which (like your said) can't form a quorum.
If you need to support 2 concurrent nodes failures you will need to increase the size of your cluster and preferably also separate Sentinel nodes from Redis nodes.