As an integral part of Windows Server 8, Cluster-Aware Updating provides a reliable, automated updating feature for server clusters. This facility permits system administrators to update clustered servers with little or no loss in availability while the update process is under way.
It is specifically intended to reduce service outages, eliminate the need for manual updating workarounds, and to simplify the cluster-updating process for administrators.
For workloads that support arbitrary process moves, such as Hyper-V live migration, Cluster-Aware Updating (CAU) is designed to exploit these capabilities so that there is no downtime for clients. The wizard makes it easy to customize updates to suit prevailing local practices, so that administrators can run custom PowerShell scripts as part of the cluster-updating process. Additionally, CAU ships with an extensible design meant to be extended and adapted by various ISVs and IHVs to build new solutions (e.g. cluster firmware updates).
Cluster-Aware Updating functionality gets installed on every cluster node as part of Microsoft’s failover clustering feature. Failover clustering tools, including CAU, may be installed on any Windows Server 8 machine even if it is not a member of a cluster or on a Windows 8 Client, as part of the Remote Server Administration Tools (here’s a link to the current version for Windows 7 and Windows Server 2008 R2; presumably a version for Windows Server 8 should be available around the GA date as well).
You can see a pretty good set of screenshots that illustrate the CAUW at work on Microsoft Cluster MVP Robert Smit’s “The System Center Connector” blog. He makes the observation that you’re best off using a management server to run the CAUW because it won’t patch the server on which the Wizard itself is running. He shows the processes and selections involved in choosing and applying updates to a server. Smit speaks favorably of its simplicity and high degree of automation.
In general, Cluster-Aware Updating both enables and automates the process of scanning for, downloading, and installing cluster updates from one of the following sources: a) Windows Server Update Services (WSUS), b) Windows Update or Microsoft Update, or c) any CAU-compatible third-party update source. Such third-party sources must develop an appropriate plug-in, which may then be installed on a computer running CAU tools. The default plug-in for Windows Server 8 supports either WSUS or WU/MU sourcing for updates. This is how the CAUW integrates directly into existing update infrastructures, and by automates the end-to-end cluster update process. See the MSDN site for sample code, and find further discussion in a video titled "Designing systems for continuous availability – multi-node with block storage" (the CAU segment begins approximately 20 minutes into the footage).
The biggest boon that Cluster-Aware Updating delivers is to enable a high-availability/failover cluster to keep running, even as updates are applied to individual cluster elements. Likewise, this tool’s support for plug-ins and automation makes it simpler to apply (or even roll back) updates to a cluster than it has ever been in previous Windows Server releases. Flexibility and ease of use are never unwelcome in server administration tools, particularly for tasks that can be as finicky or tricky as performing server cluster updates or applying patches to a cluster. I predict that this facility will be a great addition to the Windows 8 arsenal, and will help make administration of server clusters – even large ones – easier than it is today.
ABOUT THE AUTHOR
Ed Tittel is a full-time freelance writer who specializes in Windows operating systems, information security, and markup languages, who also occasionally works as a consultant and expert witness. His techtarget blogs include Windows Enterprise Desktop and IT Career JumpStart, and he also blogs weekly for PearsonITCertification.com on IT Certification Success as well.
This was first published in December 2011