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Virtualizing Exchange on VMware Provides More Recovery and Availability Options

We wanted to take a minute and respond to the recent blog post by the Microsoft Exchange team (Answering Exchange Virtualization Questions and Addressing Misleading VMware Guidance). In the post, Microsoft expresses concerns around particular VMware guidance for deploying Exchange Database Availability Groups (DAG) in conjunction with VMware HA.  We’d like to provide our perspective on this configuration and explain why it isn’t reckless (as Microsoft suggests), but all to the contrary can help our customers get greater value out of virtualizing Exchange.

The proposed solution consists of deploying Exchange DAG on a VMware vSphere cluster, and complementing DAG with VMware HA to maximize availability.

To clarify some of the apparent confusion on VMware HA in the Microsoft blog, VMware HA has nothing to do with VMotion or DRS.  VMware HA is a very simple mechanism that automatically reboots a failed virtual machine on any available host in the vSphere cluster in the case of a host failure.  From an application standpoint, the behavior of VMware HA is equivalent to a simple power-on of the machine on which the application is running.   It is completely transparent to the OS and the application.

In the physical world, when a DAG node fails, an admin will eventually power-on that node to restore the original availability protection.  VMware HA does exactly the same thing, but automatically.  Seems to us like that’s a pretty reasonable thing to do, and many of our customers agree and are happily using this in production.  Why?  For example, in a deployment with 2 database copies, if one of the DAG nodes were to go down due to a host failure, Exchange would be left ‘unprotected’ until the failed DAG node could be brought back up.  That could take quite a bit of time, relying on an administrator to detect the failure, and manually power on the failed node. VMware HA automatically takes care of that for you in the shortest time possible to restore the DAG availability protection.

Does this solution increase the cost of deploying Exchange?  No!  Compute requirements are unchanged, since VMware HA doesn’t rely on failover instances.   VMware HA also does not impact overall storage requirements.

Does this solution increase complexity?     Our customers think our solution makes Exchange a whole lot simpler.  When a DAG node fails, you no longer need to manually detect the failure and bring the node back up – VMware HA does that automatically.  And VMware HA doesn’t require any OS- or app-level configuration changes.

As to the support situation, we acknowledge that this is not an officially supported configuration under the Microsoft SVVP Program.  Should that stop all customers from using it?  Consider the following facts:

  • We have tested the configuration ourselves and haven’t seen any technical issues from powering on the DAG node VM automatically.
  • Customers are using this configuration in production with no technical issues.
  • Microsoft customers with a Premier Support agreement are entitled to reasonable support beyond specific SVVP-validated configurations.

In some cases customer needs can go beyond the vendor’s official support positions or guidelines.  In these situations, it’s up to the vendors to step up and meet those needs.  We’re extending an open offer to the Microsoft Exchange team to help them better understand, test, validate, and support this valuable solution!

Alex Fontana and Scott Salyer

(Original authors of the Exchange on VMware Best Practices and availability docs)


7 thoughts on “Virtualizing Exchange on VMware Provides More Recovery and Availability Options

  1. Jim Lucey (MSFT)

    For over 15 years our team has focused on defining system requirements and support guidelines which ensure our customers have the best possible experience deploying and managing their Exchange environments. We strongly advise customers against deploying in unsupported configurations on the promise of support from a 3rd party. We do recognize, however, that many of our customers see virtualization as an increasingly important component of their Exchange deployment plans and will continue to work with our own Hyper-V team and VMWare to provide responsible guidance which is in the best interests of our mutual customers. Despite our disagreements, we are happy to see VMWare’s enthusiasm for doing what is best for our mutual customers and look forward to working with Alex, Scott, and others at VMWare who share this common commitment.

  2. RUSerious

    Just curious, will you provide support when a customer calls PSS and they tell them to pound sound after determining VMWare HA caused their DAG to have a terminal meltdown?
    Also, I KNOW this isn’t possible (sarcasm here), but I am SURE you have put tons of regression testing and time to keep up with Exchange 2010 as RU’s and SP’s come out right? Seriously, grow up and play the game by the rules instead of saying silly things like “Customers are using this configuration in production with no technical issues. ” That is juvenile and frankly reckless professional advice.

  3. Gerhard

    Questions for MS…
    A. Are Exchange DAGs supported in VMs excluded from VMWare HA?
    B. Is it supported to restart a Dag immediately after it has been shut down (or failed)?

  4. Gerhard

    Question at Mr. Jim Lucey. How would MS even have a clue if a VMWare Exchange Dag is enabled for failover within a VMWare cluster. There is no way from within an Exchange (or any other) VM to tell. When asked the question one simply says NO….never….we do everything by the book.

  5. ChanEK

    Just thought I’d mention this (know this post is fairly old now and may not have been kept up to date) but the mentioned concerns in this post (DAG VMs on HA clusters) is NO LONGER not supported.
    As per technect, with the release of Exchange 2010 SP1 (as opposed to the RTM), all exchangne VMs including the DAG VMs are fully supported on HA (or clustered root servers) as long as the VM is rebooted post the failover (which is does with VMware HA….duh?? ).
    So a clear win for the VMware guys here…. (Not sure why the restriction was in, and is still in for RTM version but hey…sure there is a reason for MS)
    See my article for a summary of Exchange on Vmware – whats supported and whats not supported by MS at,

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