In IBM Cloud Pak for Integration (CP4I) v2021.2, which runs on Red Hat OpenShift, logging is handled using the OpenShift Logging Operator, which often utilizes Elasticsearch as the log storage backend.
For a highly available (HA) Elasticsearch cluster, the minimum number of nodes required is 3.
Elasticsearch uses a quorum-based system for cluster state management.
A minimum of three nodes ensures that the cluster can maintain a quorum in case one node fails.
HA requires at least two master-eligible nodes, and with three nodes, the system can elect a new master if the active one fails.
Replication across three nodes prevents data loss and improves fault tolerance.
Why Are 3 Elasticsearch Nodes Required for High Availability?Example Elasticsearch Deployment for HA:A standard HA Elasticsearch setup consists of:
3 master-eligible nodes (manage cluster state).
At least 2 data nodes (store logs and allow redundancy).
Optional client nodes (handle queries to offload work from data nodes).
Ensures HA by allowing Elasticsearch to withstand node failures without loss of cluster control.
Prevents split-brain scenarios, which occur when an even number of nodes (e.g., 2) cannot reach a quorum.
Recommended by IBM and Red Hat for OpenShift logging solutions.
Why Answer C (3) is Correct?
A. 1 → Incorrect
A single-node Elasticsearch deployment is not HA because if the node fails, all logs are lost.
B. 2 → Incorrect
Two nodes cannot form a quorum, meaning the cluster cannot elect a leader reliably.
This could lead to split-brain scenarios or a complete failure when one node goes down.
D. 7 → Incorrect
While a larger cluster (e.g., 7 nodes) improves scalability and performance, it is not the minimum requirement for HA.
Three nodes are sufficient for high availability.
Explanation of Incorrect Answers:
IBM Cloud Pak for Integration Logging and Monitoring
OpenShift Logging Operator - Elasticsearch Deployment
Elasticsearch High Availability Best Practices
IBM OpenShift Logging Solution Architecture
IBM Cloud Pak for Integration (CP4I) v2021.2 Administration References:
