In my last post about Exchange migration, I wrote about the preparation of the Active Directory. Before I give a rough guide through the migration process I want to talk about the possibilities of virtualizing Exchange Server 2010. There are two reasons why I think it is necessary to bring this point up: First, there are still quite a few administrators that have a deep aversion to virtualization. Second, although virtualization is widely used today, there are a few things you have to consider before you should deploy Exchange 2010 on a virtualized machine. Exchange 2010 is ready for virtualization, so you can install every role on virtualized guests. Only the Unified Messaging Server Role needs to be installed directly on the hardware.

For those who are still skeptical about running a business-critical application like Exchange in a virtualized environment, I just have to say that it works; indeed, it works very well. Besides that, there is no difference between running Exchange Server 2010 on a hardware machine or a virtualized machine, as long as you follow some guidelines. It even has some advantages: If you want use the DAG feature of Exchange 2010 you need two Server and two Windows Server 2008 R2 Enterprise licenses. If you only have a midsized company, the chances are big that the resources of the two Servers are not close to being utilized properly. The Windows Enterprise license allows you to run up to four software instances at a time in a virtualized environment under one license. So you could have up to eight virtualized machines running Windows Server 2008 R2 Enterprise with the two licenses you need for a DAG. Isn't that alone reason enough to virtualize Exchange 2010?

But the focus of this post is not to convince you of going virtual, but to give you some help in deploying the virtual environment properly. Because you already have a Windows Server 2008 R2 Enterprise license, and because Hyper-V is a great hypervisor, I recommend using Hyper-V R2 as the host system. But you are not limited to Hyper-V. If you favor other virtualization solutions, like VMware ESX, Exchange 2010 should run on them flawlessly, as long as the product is part of the Server Virtualization Validation Program.

The most important point you have to consider when going virtual is performance, because an improperly deployed virtualized Exchange system can result in sluggishness and instability. There are just a few points you have to consider when going virtual:

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  • The virtual hard disk has to be either fixed sized or a passthrough hard disk. Passthrough disks are the faster option, and should be used for storing the mailbox. If you plan to use a SAN, Microsoft recommends using a separate LUN for the host server, the guest server and the virtual hard disk on which the Mailbox is stored.
  • Hyper-V offers the option to take snapshots from guests. This is great feature for testing purposes, but you should never use this feature when performance is important, because after you have taken a snapshot, performance will drop a lot. Furthermore, reverting to a snapshot is not supported by Microsoft.
  • Allocate sufficient memory for the host system. 1 GB of RAM may be enough, but I would reserve at least 2 GB of RAM for the host system.
  • You can have a maximum of two virtual processors for every physical core. One physical core is reserved for the host system. So if you have one quad core processor you can assign up to six virtual processors to your guest systems. The amount of virtual processors per guest is limited to four, though.
  • For managing your host, you should reserve one NIC. Also, if you run a failover cluster, you should have a dedicated NIC for this purpose. Depending on the network bandwidth the guests need, it might be necessary to use more than one NIC for the guests.
  • The virtualization host should be dedicated to serve the virtualization environment, so no other services should run on it.

If you follow these recommendations, you have the basement for a stable and fast virtualized Exchange 2010 environment. Nonetheless, you have to plan the amount of servers and their resources correctly not to run into any problems.

8 Comments
  1. Bret Fisher 11 years ago

    If your running Hyper-V R2, there is very little difference (read: academic only) between fixed disk and passthrough based on a new whitepaper MS released. Also, Server 2008 R2 greatly improves performance of all VHD types but most notably fixed and dynamic disks.

    search "vhd performance white paper" from 2010

    Lastly, even though UM on virtual is discouraged, it does work as long as you don't overtax the hardware, which will cause slow response to calls. The core issue (as I understand it) is the voice services were licensed/bought by a 3rd party, who hasn't fully vetted virtual yet.

  2. ElJefe 11 years ago

    Exchange when using dynamic disks is not supported by Microsoft.

  3. Bret Fisher 11 years ago

    Yes it may say that in the requirements but it functions just fine if you have enough disk I/O to back it up. If in a pinch and fixed just won't fit your backups or server space and performance isn't an issue then it "will work" and MS Product Support will always take your call and help the best they can.

    Sometimes it helps to understand what "not supported" means. To Microsoft that means they'll help you all the way up to "we tried everything else, but we think the thing we said wasn't supported is your problem".

  4. Eljefe 11 years ago

    No one is saying that it won't work, however it is foolish to recommend that an enterprise class organization use a non-supported configuration. Of course Microsoft will always take the call. Why wouldn't they? They are getting paid to take the call. At the end of the day dynamic disks are still not supported in any way, shape, or form. Microsoft Support is very quick to blame third-party products and unsupported configurations when diagnosing a problem. I would never put myself in a position in which I have to tell my CEO that I am at the end of the road with Microsoft’s support team because I deployed an unsupported Exchange environment.

  5. Andreas Erson 11 years ago

    Just convert the supposed dynamic disks to fixed and your road just got a lot longer...

  6. Eljefe 11 years ago

    So Andreas, why deploy dynamic disks at all? That is the question and the main point of my argument. In an organization where space is not a concern there is neither a good nor legitimate reason to deploy Exchange with dynamic disks. That was the only argument I was making. I understand that it can be done and that it works well. It is never wise to deploy an environment based on an unsupported configuration.

  7. Andreas Erson 11 years ago

    Eljefe: I agree with you regarding deploying Exchange 2010 using fixed or pass-through disks.

    But I disagree with you that you need to tell your CEO that you are at the end of the road with Microsoft's support since you can easily correct the mistake to deploy using dynamic disks by just converting them to fixed. Convert, continue to solve any problem with Microsoft and there's simple no need to escalate it to your CIO/CEO.

    Basically, it's not the end of the world if you made the mistake to deploy using dynamic disks since you can easily correct that.

  8. Gonzalo 11 years ago

    Problem deploying ESXi 4.0 +Windows Server 2008 R2+ Exchange 2010, vm freeze randomly, it's a bug

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