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Raw Exchange
Virtualize your Exchange server? It's almost a no-brainer.
- By Greg Shields
- 05/12/2008
When people consider the virtualization question, especially in SMB and mid-market IT environments, one of the most critical servers under consideration can be the mail server. E-mail has become such a critical component of any IT environment, that in many ways its uptime is more important than any file server or database server in the environment.
At the very least, it's when the mail server goes down that people scream the loudest.
Virtualizing Exchange is a great solution for adding resiliency for this critical service. An unplanned hardware outage can be reduced to a restart on an available virtual server. Snapshotting technology present in essentially all virtualization platforms gives administrator the warm fuzzy that a poorly written patch can be fixed with a "Revert to Snapshot."
But Exchange data stores can be huge, and wrapping those gigantic data stores into a virtual disk file can introduce problems all its own -- not the least of which affect performance and scalability.
One answer to these problems lies in keeping Exchange data files out of virtual disk files and connecting to them through the LUN mapping features of your virtualization platform. Direct LUN mapping is slowly becoming a part of all virtualization products. This capability allows for a disk's LUN to be directly plugged into the virtual machine as if it were a physical connection. Files on that LUN typically remain in a file system like NTFS rather than being encapsulated into a virtual disk format.
Other products have had workarounds for a while, such as VMware's Raw Device Mappings (RDMs). An RDM is effectively a symbolic link within VMware's proprietary VMFS file system that points to another LUN elsewhere. That remote LUN runs a different file system such as NTFS. Click here for a good explanation of how to set this up.
While virtual file encapsulation tends to work well for information stores that are smaller in size, these alternate architectures and direct mappings may work better in certain circumstances. Your mileage will vary, so test any solutions before you implement any architecture in your virtual environment.
About the Author
Greg Shields is Author Evangelist with PluralSight, and is a globally-recognized expert on systems management, virtualization, and cloud technologies. A multiple-year recipient of the Microsoft MVP, VMware vExpert, and Citrix CTP awards, Greg is a contributing editor for Redmond Magazine and Virtualization Review Magazine, and is a frequent speaker at IT conferences worldwide. Reach him on Twitter at @concentratedgreg.