Can you run an elasticsearch data node after deleting the data folder?

Question

I am running a three node Elasticsearch (ELK) cluster. All nodes have all and the same roles, e.g. data, master, etc. The disk on node 3 where the data folder is assigned became corrupt and that data is probably unrecoverable. The other nodes are running normally and one of them assumed the master role instead.

Will the cluster work normally if I replace the disk and make the empty directory available to elastic again, or am I risking crashing the whole cluster?

EDIT: As this is not explicitly mentioned in the answer, yes, if you add your node with an empty data folder, the cluster will continue normally as if you added a new node to the cluster, but you have to deal with the missing data. In my case, I lost the data as I do not have replicas.

Answer 1

Let me try to explain that in simple way.

Your data got corrupt at node-3 so if you add that that node again, it will not have the older data, i.e. the shards stored in node-3 will remain unavailable for the cluster.

• Did you have the replica shards configured for the indexes?
• What is the current status(yellow/red) of the cluster when you have node-3 removed?

If a primary shard isn't available then the master-node promotes one of the active replicas to become the new primary. If there are currently no active replicas then status of the cluster will remain red.