The Microsoft Stack: Windows Server 2008 Clustering Designed to Overcome Usability Barrier

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The Microsoft Stack: Windows Server 2008 Clustering Designed to Overcome Usability Barrier
By Patrick Hynds

August 1, 2008 —

Reliability is important to all organizations, but in some cases it is life and death. Earlier this year I helped a health-care organization recover from an outage that had an entire hospital working without crucial data they would rather not lose access to while treating patients.

The offending system was a Windows 2003 Server cluster hosting SQL Server, as well as other services. I was called in not to fill a gap in technical depth, but because Microsoft clusters are a bit of a black art if you don’t deal with them regularly. We were able to recover the offending node and restore the corrupt shared registry in a very short time, but it highlighted the real barrier to why more organizations are not using Windows clusters more widely, and that is usability.

Cluster servers started with a product years ago that was code named Wolf Pack, a very World War II-style code name, and has evolved to be quite powerful but not terribly easy to use. The good news is that ease of use is a major goal with the new version of clustering soon to be available in Windows Server 2008.

Before I dive into the promised improvements, let’s review the concepts behind Windows Clustering, starting with the quorum drive. To do this, let's think of two people working to ensure a critically ill patient receives a high level of care for 24 hours. The key element to ensure the continuity of care is that both caregivers share a common knowledge of the situation at any given moment and also that they know who is actually supposed to be in charge at any given time, to avoid such potentially deadly events as giving overdoses of medicines.

The quorum drive provides the storage location that both nodes share (by turn), so that when one fails, the other can pick up where things left off. There are also shared resources that fail back and forth as the active node changes. For this reason, any stateful objects like files or logs are stored in a place that the active node can assert control over and pick up where the failed node left off.

There are many great improvements to clustering with Windows Server 2008 that will likely drive many more organizations to start leveraging Windows-based clusters. The old one-off interface is replaced with the more familiar Microsoft Management Console (MMC) interface, and there is a greatly simplified user interface for both creating and managing clustering, thanks to a wizard that does away with the arduous task of defining dependencies and groups.

This change will bring clustering to the masses, as the simplifications made to SQL Server between version 6.5 and 2000 have led to SQL Server becoming so easy to use and therefore so ubiquitous.

Another aspect of setting up clusters is ensuring that the servers that you plan to enlist as nodes in the cluster are online. The Validate tool will verify that the proper software is installed and consistent across cluster nodes (up to and including OS service packs and hotfixes), and that network connections are correct and alive.

Validate is a bit of a double-edged sword, since you can still install and make functional a cluster that fails some of the less critical validations of the Validate tool, but Microsoft support will not work on a cluster that fails any of the Validate tool tests, so it is best that you take the time up front to ensure that your nodes pass all the tests.

As you can probably deduce from that last statement, you can run the Validate tool as a diagnostic tool after the cluster is running. Very often this would have saved some of my clients from having to call me in when things have gone wrong with prior versions of Windows clustering.

Other welcome improvements include remote management via MMC with Remote Server Administration tools, command-line and Windows Management Instrumentation support, and the ability to perform migrations of Windows 2003 Server clusters.

The only downside I see to Windows Server 2008’s new improvements to clustering is that my rate for consulting with it will have to drop, because the black art has gone out of it. The bright side is that the world will likely look to people with lots of cluster experience far more often as higher reliability gets far easier to attain. After Windows Server 2008 ships, I hope to revisit this topic to discuss areas where you still might get into trouble, but I am hoping that will prove to be a short list.

Patrick Hynds, president of CriticalSites and a Microsoft Regional Director, can be reached at phynds@criticalsites.com.

Related Search Term(s): clustering, Windows Server, Microsoft

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