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Editing Registry Settings in a Microsoft Cluster

I wanted to post a quick blurb here about making registry edits on nodes of a Microsoft cluster. This is especially handy when attempting to change paths that are tied to a cluster resource or service.

You must make sure that the cluster resource is online (or that the service is running) when you make the registry edits. You must make the edits on the active node of the cluster as well. After you have made the registry edits you may take the resource offline or stop the service. Now you restart the service or bring the cluster resource online and the most recent registry settings are passed back to the registry (the changes you recently made.) The changes will also be propagated to the passive node at the next fail over.

This is a key issue that even Microsoft tech support seems to ignore at times. If you make changes to a registry key when the service is stopped or cluster resource is offline, when you restart the service or bring the cluster resource online, it will overwrite your changes with the last known registry settings for that service or resource before it stopped or went offline. This can often put system administrators in a loop of changing registry keys and then having them revert. The reason for this behavior is that in a cluster, the cluster's Registry Checkpoint is in a special area of the quorum. Every time a service is restarted or a cluster resource is brought online, the Registry Checkpoint information is written back to the active node. Every time a service is stopped or a cluster resource is taken offline, the current registry information residing in the active node is written back to the cluster's Registry Checkpoint.

With that said, it makes perfect sense that services must be running in order for your registry change to be written into the cluster's Registry Checkpoint in the quorum and thus propagated from that same Registry Checkpoint.

I hope this saves someone out there a lot of hair pulling some day.

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