GSX Blog

The DAG Witness server finally supported in Azure

Posted by Juliette Ollagnier on Tue, Jan 13, 2015


describe the imageOur friend Scott Schnoll, Office 365 Senior Program Manager at Microsoft, announced during a session in Teched Barcelona that Exchange will soon support Azure VM as a Witness Server. The wish came true! Microsoft just announced support for the most awaited feature "Witness Server in Microsoft Azure". It is a nice option to have to allow automatic failover when you don't have a 3rd physical site to use. This new enhancement will make Exchange DAGs more robust by building one more layer of high availability, and assists the automatic datacenter failover during Disaster Recovery scenarios in a site-resilient Exchange Infrastructure.

The key to make this work is the new enhancement "Multi-site VPN support" made available to Azure in June 2014. Microsoft Azure introduced multi-site VPN support, which enabled organizations to connect multiple datacenters to the same Azure virtual network. This change also made it possible for organizations with two datacenters to leverage Microsoft Azure as a third location to place their DAG witness servers.

More information with detailed walk-through is available in this TechNet article, written by Jeff Mealiffe, Principal PM Manager at Microsoft.

Automatic datacenter failover in Exchange 2013 requires three physical sites, but many of our customers with stretched DAGs only have two physical sites deployed today. By enabling the use of Azure as a third physical site, this provides many of our customers with a cost-effective method for improving the overall availability and resiliency of their Exchange deployment.

You can learn more about the deployment and configuration process, as well as learn about our best practices in the TechNet Library article.

It’s important to remember that deployment of production Exchange servers is still unsupported on Azure virtual machines, so it’s not yet possible to stretch a DAG into Azure. This announcement is limited to deployment of a file share witness in the Azure cloud. Also note that this is not related to the “Cloud Witness” feature in the Windows Server Technical Preview. Stay tuned for future announcements about additional support for Azure deployment scenarios.

A DAG is the fundamental component of the high availability and site resilience framework built into Microsoft Exchange. It hosts a set of databases and provides automatic database-level recovery from failures that affect individual servers or databases. Because it provides a global service of Mailbox availability, it has to be considered as an entity itself and not only as a collection of servers.

Managing the DAG is critical as it ensures High Availability. GSX Solutions provides a monitoring solution to check the service delivered by the Exchange. GSX solution send IT administrators proactive alerts for him to anticipate potential slowdowns and outages.

What does GSX do?

  • Database Failover alert: receive an alert as soon as a failover occurs in the DAG
  • DAG statistics: availability and usage of the database inside the DAG
  • DAG availability status (DAG up or down) available on main view
  • Deep replication tests

Read more about >" target="_self">GSX Monitor and Analyzer for Microsoft Exchange >>

Tags: Exchange reporting, microsoft azure, Exchange monitoring, DAG monitoring, database availability group