Tuesday, October 22, 2013

Why My DAG is Not Stable?

One of the great feature of Exchange Server 2010 and 2013 is the Database Availability Groups (DAG), Environments which deployed DAG can minimize downtime by leveraging the great feature of automatically mounting the Passive copies when Active goes down due to an unexpected Event and thus maintaining high availability with no end user downtime.

I have already written few Articles specifically over DAG and Exchange Server High Availability which talks more over this feature and they all can be found here. Today I came across two important Articles from our Exchange Experts Tony Redmond on Windows IT Pro and the latest EHLO Blog post from Mike O'Neill - MSFT which made me write this post.

Both of these Articles are really great enough and provides us some overview of the potential causes that makes our DAG Environment to go unstable other than some common events which causes the Passive Database to get activated by the Active Manager.

In the below Post Tony explains how the new Managed Availability feature Introduced with Exchange Server 2013 causes our DAG to go unstable due to other potential causes, unlike 2010, where we have now this new Managed Availability component which closely talk with the Active Manager and issues mount request to activate the passive copies when some thing goes wrong with the server holding the Active database copies. Also he has explained how Admins can control and know how to monitor when some changes occurs within the DAG distribution and fix it accordingly and much more in detail.

Read the post here for more detail: The influence Managed Availability has over DAGs that you might not realize

Now, let's come to the second article from EHLO Blog in here Mike explains about one more hidden cause on NIC Card power management settings that would eventually make our DAG unstable based on his real time findings and suggested us how to fix the issue proactively and make our DAG Environment stable.

You can read the following blog post to know more : Do you have a sleepy NIC?

These blog posts are quite significant to know more over DAG instability and react accordingly.

Thanks once again to Tony and Mike.

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