Problem Description

Current Atlassian documentation does not provide a strict "one-size-fits-all" guideline for the node count of the Jira DC cluster. We do offer some general clustering recommendations and best practices through some official documentation and resources. Like for example, Running Jira Data Center in a cluster

Your Data Center license does not restrict the number of nodes in your cluster. The right number of nodes depends on the size and shape of your Jira instance, and the size of your nodes. See our Jira Data Center size profiles guide for help sizing your instance. In general, we recommend starting small and growing as you need.

Or from Scaling Jira Data Center:

Adding nodes

Since each node communicates with the others, adding nodes to your cluster also adds network traffic. It's important that you use network monitoring tools to make sure your cluster can handle the increased traffic both between nodes, and also to your database and shared file system. You can run network monitoring and performance tests on your application using these performance testing tools to help understand the total number of nodes your environment can gracefully handle. Atlassian's internal testers have tested up to 4 application nodes for Jira Data Center. If you find that you are hitting a maximum number of nodes in your cluster, you might consider upgrading (also known as "vertically scaling") your existing nodes to get more capacity and performance.

However, this advice is general and doesn't provide Jira administrators with any best practices recommendations of how to evaluate the most suitable size of the cluster based on the size/workload of their Jira instance.

Suggested Solution

It would be beneficial to have a single document that contains current (considering the latest Jira version) recommendations regarding the number of nodes in the cluster. This should help Jira administrators to have some knowledge they could rely on during horizontal scaling of the Jira cluster.