CAU is an external cluster-updating solution that is layered on top of clustering APIs and Power Shell cmdlets.
As such, CAU can coordinate updating for any clustered application that is configured in a Windows Server failover cluster. By default, CAU is configured with a plug-in that uses the Windows Update Agent (WUA) utility APIs on the cluster nodes.
However, CAU includes a second plug-in that you can select to apply hotfix updates.
This hotfix plug-in can also be customized to apply non-Microsoft driver, firmware, and BIOS updates. If the cumulative updates are general distribution release updates or LDR updates, CAU can apply them. CAU supports the following updating modes, both of which allow updates to be scheduled: Self-updating Enables the cluster to update itself according to a defined profile and a regular schedule, such as during a monthly maintenance window.
When CAU finishes updating a cluster node, it attempts to fail back previously hosted clustered roles to that node.
CAU relies on clustering APIs to fail back the resources to the beginning of the pause process.
Although the CAU UI can start without the credentials, it prompts for the cluster administrative credentials when it connects to a cluster instance to preview or apply updates. CAU comes with Power Shell cmdlets that offer a rich set of scripting options.You can also start a Self-Updating Run on demand at any time.To enable self-updating mode, you must add the CAU clustered role to the cluster.The clustering API implementation selects the target nodes by relying on internal metrics and intelligent placement heuristics (such as workload levels) across the target nodes.CAU doesn't load balance the clustered nodes, but it attempts to preserve the distribution of clustered roles.