Does JIRA support clustering?
No, we've considered this in the past and have chosen to not implement the JIRA clustering feature request.
If you are deploying JIRA to a clustered environment, please note that this is not supported. You may also wish to ensure that the JIRA Webapp is deployed to only one node in the cluster. Most clustered applications support this feature (e.g. WebLogic). Also ensure that your load balancer(s) are configured to direct all requests for JIRA to the correct node in the cluster. Again, none of this is supported.
If you wish to run JIRA across multiple nodes you will need a license for each node.
If you are interested in clustering for hardware failover, you can configure a distributed database, load balancer front-end and two separate servers. The primary JIRA instance runs on the main server, while the second server contains an unstarted, free development license instance of JIRA. The load balancer directs 100% of requests to the primary as long as it is responsive, but if the primary server goes down, the load balancer starts the backup instance and directs all requests there until manually reset. Again, none of this is supported by Atlassian.
While Atlassian itself does not support JIRA clustering, Scarlet is a custom edition of JIRA that does support the deployment of JIRA to multiple nodes.