Cluster Aware Update, sometimes referred as CAU, was first introduced in Windows Server 2012 for failover clusters. This feature automates the software updating process on clustered nodes while maintaining the availability.
How CAU works?
CAU works automatically on cluster nodes running Windows Server 2012 or Windows Server 2012 R2. During the update process, the following events take place:
CAU is an automated feature that enables you to update clustered servers with little or no loss of availability during the update process. During an Updating Run, CAU transparently performs the following tasks:
- Puts each node of the cluster into “maintenance mode”
- Moves the clustered roles off the node
- Installs the updates and any dependent updates
- Performs a restart if required
- Brings the node out of maintenance mode
- Restores the clustered roles on the node
- Moves to update the next node
Note: Hyper-V VMs are live migrated to available Hyper-V Node in the cluster maintaining the availability of the virtual machines.
About Nirmal Sharma
Nirmal is a MCSEx3, MCITP and was awarded Microsoft MVP award in Directory Services. He is specialized in Directory Services, Microsoft Clustering, Hyper-V, SQL and Exchange and has been involved in Microsoft Technologies since 1994. In his spare time, he offers technical help by writing tips and articles. Nirmal can be reached at firstname.lastname@example.org.