Is Microsoft really saying "don't virtualize" Exchange?

Happiness is a warm virtual Exchange server. Or so it used to be (for some - not for me) because virtualization was seen as a great solution for many things. Microsoft eventually supported virtual Exchange servers and we've had the choice between virtual and physical for three versions now. But it seems to me that some of the urge has gone out of the virtual bandwagon. Microsoft prefers virtual servers, there are many caveats and can't-do with virtual Exchange 2013, and cost is a real issue - and some of those who would have virtualized in the past now use Office 365. So has virtualized Exchange any future?

Microsoft’s embrace of simplicity in all things to do with Exchange 2013 and an increasing focus on utilizing low-cost hardware might have the unexpected side-effect of turning customers away from virtualization. If so, it will reverse a trend that had gathered pace ever since Microsoft first saw the light of the virtual day after Hyper-V appeared. It’s true that their policy toward virtual servers had moderated through the support of the combination of Exchange 2003 SP2 and Microsoft Virtual Server 2005 R2 in 2006, but full liberation of hypervisors had to wait until Exchange 2007 SP1 on Windows 2008 (using 64-bit servers, of course).

Over the six years or thereabouts since, virtual Exchange servers have become pretty popular on both VMware and Hyper-V and, to the credit of the Exchange development group, they have made Exchange a well-behaved citizen on virtual platforms. Sure, Exchange 2013 likes to be allocated static resources and doesn’t agree with dynamic memory and the like, it only supports movement between hosts using features like Hyper-V Live Migration, NFS storage remains unsupported, and snapshots (especially of running DAG member servers) are right out, but the list of cautions and restrictions published by Microsoft for virtual Exchange 2013 servers is pretty pragmatic and easily understood.

All of this seems reasonable for those contemplating using virtual servers as the basis for their deployment. Until, that is, you consider three pieces of information. First, there’s Microsoft’s Preferred Architecture for Exchange 2013, which states:

In the PA, all servers are physical, multi-role servers. Physical hardware is deployed rather than virtualized hardware for two reasons:

The servers are scaled to utilize eighty percent of resources during the worst-failure mode.

Virtualization adds an additional layer of management and complexity, which introduces additional recovery modes that do not add value, as Exchange provides equivalent functionality out of the box.”

Fair enough. Microsoft selects physical hardware for a particular reason, something that is understandable when you consider that a lot of their operational experience with Exchange is gained from Exchange Online, where virtual servers are not used and the degree of automation and standardization that is practised is at a level that the average deployment would use.

Then we consider the points made by Jeff Mealiffe at his excellent “Exchange 2013 Virtualization Best Practices” MEC session. If you wandered into the room and had never contemplated the virtualization of Exchange before, you would probably have been left with an impression that this is not something that intelligent administrators do (at least, not for the servers where the mailboxes of their friends are located). Lots of restrictions, an emphasis on the complexity that the hypervisor brings to the operational environment, and a warning that you should only virtualize if you’re going to get something out of the exercise. In other words, don’t embrace virtualization unless it saves you money or delivers some other measurable advantage.

I thought the session was terrific as it was packed with information and contained some very well-founded points. There was enough there for anyone to be encouraged to think through their options so that a decision to virtualize was taken for the right reasons. You can listen to Jeff’s talk (use the link above) to make your own mind up. I’ve always preferred physical mailbox servers (I can live with virtual CAS or edge transport servers), so there’s a fair chance that I might be biased on this point.

But the third factor that no one really seems to talk about is the cost of the virtual platform. Exchange 2013 is a bit of a resource hog (no surprise there), so some pretty well-configured servers are required for the virtual hosts. Now factor in the need for several virtual hosts to ensure that your highly available mailbox servers are not rendered useless when an entire DAG is taken offline through the failure of one host. To avoid putting your eggs in one proverbial virtual basket, you need to distribute the virtual Exchange servers across multiple hosts, all of which are replete with CPU, disk, and memory. Add in the costs of the hypervisor, including training and support and perhaps some third-party software to handle backups and other mundane tasks, and you might be looking at additional cost mounting to tens of thousands of dollars. At least, that’s what I am being told by people who know a lot more about this topic than I do.

Another influence to factor in is the movement to the cloud. It seems logical that many of the companies that might have virtualized Exchange in the past to make better use of available resources will end up using Office 365. If you only have two or three hundred mailboxes in the company, Office 365 is probably the best choice for you.

If you put Microsoft’s architectural preference for physical servers together with their warnings of the complexities that a hypervisor brings and the additional cost incurred for virtualization, you have a combination that screams “don’t do this.” At least, don’t do virtualization unless you know what you’re doing, you have a good reason for virtualizing Exchange, your operational situation is mature enough to cope with the additional complexity, and you know how to harness the business and technical benefits that virtualization can bring.

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Discuss this Blog Entry 4

on Jun 19, 2014

I've only worked in what I would call Enterprise (Exchange deployment is around 14,000 mailboxes) for just over a year and I came from supporting SMB, so it is still a bit new to me.

But the organisation I work for has a deep investment in virtualisation (over 850 VMs) and it seems difficult to be able to show management that there are still use cases for physical machines. Our 2013 environment is fully virtualised because there was no scope in the budget for physical machines and it was not something that was considered even after feedback from the technical team.

I'm not sure how everyone else goes, but I suspect this might be a failry widespread issue.

Our SQL DB admin has similar issues, he has outlined the potential performance and overhead issues with having virtual SQL machines but still can't seem to get funding for good redundant physical machines.

It almost makes me wonder if the marketing of virtualisation over the last 5 years has left management with a 'this is the be all and end all' and now we find ourselves in a difficult position to try and get funding for physical boxes (apart from VM Hosts).

Or maybe I am just unlucky :)

on Jun 19, 2014

Hi Matt, I don't think you were unlucky. Many people in the industry were smitten by the notion that you could virtualize everything and gain lots of advantages. This was a valid assertion in some ways and still is today in the right circumstances, but I think technology has moved on and the availability of low-cost physical hardware and applications that take advantage of those configurations should force us to take a new look at the options available for deployment. In some cases, the right decision will be to remain with the virtual platform because this aligns well with the business and technical strategy. In others, it won't. And in all cases, anyone who virtualizes simply because "it seems like the right thing to do" or "because everyone else is doing it" is going down a very bad path.

on Jun 19, 2014

I came from a large 35,000 mailbox Virtual Exchange 2010 environment to a smaller 500 mailbox Virtual Exchange 2010 environment. On both fronts I never noticed an issue. I moved the 500 Mail Box company to Hyper-v again with no issues. We are running a DAG (located at a DR) that is all virtual in a Hyper-V Failover Cluster. Again never an issue, no pressure on CPU or Memory (4 host with 192GB of RAM). Now in our HQ we only have 65 servers total all VM. So perhaps that scenario does't = what your concerns are about. But we also have 2 SQL servers (also in HA) that are Virtual running. We use Veeam and System Center to Monitor again with never an issue. So I am unsure of the alarm. Deployed Exchange 2013 to our Virtual Test and plan on rolling that our in the coming months.

on Jun 19, 2014

To be clear, I have no problems with a decision to virtualize an application, provided that the decision is taken with sufficient reason to back it up. And I have no problem with a deployment of VMware or Hyper-V for Exchange providing that the right resources are used, the right expertise is available, and the right operational processes are used. There is no alarm here, but there is a question over Microsoft's view on the topic. They prefer physical hardware and they use physical hardware for Office 365. We might conclude that the application is therefore tailored for that platform - logical when you look at the changes to disk I/O over the last decade. So again, if you do virtualization "right" and for the right reasons, you'll probably have no issues as you report... but the development group is not on your side... or so it seems.

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Tony Redmond is a senior contributing editor for Windows IT Pro and the author of Microsoft Exchange Server 2010 Inside Out (Microsoft Press) and Microsoft Exchange Server 2013 Inside Out: Mailbox...
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