Chapter 25: Performing a Rolling Upgrade

Overview

One of the greatest maintenance benefits of TruCluster Server is the rolling upgrade. Performing a rolling upgrade allows for the update of the operating system and the cluster software without having to take down the cluster. This unique ability contributes to one of TruCluster Server's primary themes – high availability. In this chapter, we will discuss how to perform a rolling upgrade with little or no service downtime in the cluster.

So you're probably saying to yourself, "What the heck is meant by ‘no service downtime in the cluster?’ There's no way that this can be accomplished on a UNIX system." We're here to assure you that this is precisely what happens. During a rolling upgrade, one cluster member at a time is upgraded. As soon as the upgrade is complete, that cluster member is returned to operation and then another member of the cluster is upgraded. The impact on users accessing services on the cluster is minimal and in most cases, users are not even aware that a rolling upgrade is in progress.

If you think about it, the designers of the TruCluster Server software were ingenious for allowing the operation of a cluster in a mixed-version environment for the operating system and the cluster software components.