Cisco IT maintains about 21 Cisco Unified Communications Manager (UCM) clusters to support 150,000 hardware phones and 51,000 software phones used by our global employees, contractors and contact center agents. In general, Cisco IT likes to stay up to date, and upgrades to most major releases of the Cisco UCM as soon as possible – frequently this occurs before the code is available to our external customers. We do this to take advantage of new features and to help the product developers identify needed improvements before the release is made available to customers.
For major releases, we spend a lot of time in planning the upgrade, especially if it requires configuration or design changes. We also review minor releases, including engineering specials and patches, to determine if they resolve an issue or offer a bug fix that is essential to our environment. Our typical process for planning and implementing a major Cisco UCM upgrade globally, once we decide to deploy it, requires 8-9 weeks in total. However our architect and design engineers are always looking ahead to new major releases.
We don’t upgrade all of our Cisco UCM clusters at the same time. We typically start by upgrading a few small clusters so we can familiarize ourselves with the version, and resolve any issues before we upgrade the larger clusters. Our largest clusters in San Jose and Europe approach the limits of our current product capabilities, so we are especially diligent in making changes to them.
Our current upgrade process for CUCM release 5.(x) and above could be described as “upgrade first, switch over later.” We upgrade the inactive partition without impact to the system still running on the active partition. Once complete, we switch over to make the new version active. Depending on the size of the cluster, we can perform the upgrade and the switchover in one maintenance window. For our largest clusters, we usually do the upgrade on a Thursday night and the switchover the next day, on Friday night.