Updating system specification
Cluster-Aware Updating (CAU) is a feature that coordinates software updates on all servers in a failover cluster in a way that doesn't impact the service availability any more than a planned failover of a cluster node.For some applications with continuous availability features (such as Hyper-V with live migration, or an SMB 3.x file server with SMB Transparent Failover), CAU can coordinate automated cluster updating with no impact on service availability. CAU supports updating Storage Spaces Direct clusters regardless of the deployment type: hyper-converged or converged.It's important to configure these tools so that they don't have overlapping coverage of the same servers in any datacenter deployment, including using different Windows Server Update Services servers.This ensures that the objective behind using CAU is not inadvertently defeated, because Configuration Manager-driven updating doesn't incorporate cluster awareness. For running the CAU tools, CAU needs administrative credentials on the local server, or it needs the Impersonate a Client after Authentication user right on the local server or the client computer on which it is running.
When the software updates are complete, CAU resumes the node and the clustered roles fail back to the updated node.
The WUA infrastructure can be configured to point to Microsoft Update and Windows Update or to Windows Server Update Services (WSUS) as its source of updates. By default, CAU is configured with a plug-in that uses the Windows Update Agent (WUA) utility APIs on the cluster nodes.
The WUA infrastructure can be configured to point to Microsoft Update and Windows Update or to a local Windows Server Update Services (WSUS) server as its source of updates. Limited distribution release (LDR) updates, also called hotfixes, are not published through Microsoft Update or Windows Update, so they cannot be downloaded by the Windows Update Agent (WUA) plug-in that CAU uses by default.
You can start an Updating run through the Cluster-Aware Updating window or by using the Invoke-Cau Run Power Shell cmdlet.
Remote-updating is the default updating mode for CAU.
However, CAU includes a second plug-in that you can select to apply hotfix updates.