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.
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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.