Have you ever installed Exchange 2010 on a Windows 2008 R2 server that came from an image, gotten all the way through installation and then discover that you can’t create the DAG because the OS is installed as Standard Edition and not Enterprise Edition (Entperprise being required for Cluster services to support the DAG).
It’s really disheartening to think you have to start over with re-installing the operating system.
Well, you don’t have to. Windows 2008 R2 comes with a tool called DSIM – the Deployment Image Servicing and Management tool. One of this tools amazingly useful features is the ability to upgrade the installed edition of the operating system without media.
To verify/determine the current edition, from a command line type:
DISM /online /Get-CurrentEdition
To upgrade the current edition to Enterprise, from a command line type:
DISM /online /Set-Edition:ServerEnterprise /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
Once you’ve upgraded the OS edition to Enterprise, you can re-install Exchange and create a DAG.
You can find out more about this tool from this TechNet article.