Discussion on:

Migrating to Exchange 2010: Fundamental decisions

You made the statement:

In fact, Exchange 2010 does not require Windows clustering or SAN shared storage for any high availability feature.

This is incorrect. The mailbox server role still uses Windows Failover Clustering for fault tolerance. The difference is that Exchange automatically configures it and manages it. You still need the Enterprise version of Windows for the mailbox servers because Windows Failover Clustering is not available in the Standard version of Windows Server.

Hi don@, you are correct that the Add-DatabaseAvailabilityGroupServer cmdlet automatically configures a cluster object that represents the DAG. The networking piece of DAG group failover across subnets is handled automatically by cluster services and does require the Enterprise version of Windows Server, thanks for pointing out this important license consideration. The good news for network administrators is they are freed from managing the cluster service since DAGs have no clustered applications, services, or storage resources.

I think it might be good to consider some of the following items as well:
- If you want to create a CAS Array, you will need Windows server 2008 r2 Enterprise
- An Exchange 2010 Enterprise CAL will be required in addition to a Standard CAL if you wish to use the Archiving, Legal Hold / Search and Unified Messaging features see this link: http://www.microsoft.com/exchange/en-us/licensing-exchange-server-email.aspx
- Exchange 2010 SP1 removes the GUI interface to config Manage Folders carried over from Exchange 2007. This is not an issue if your migrating from Exchange 2003.
- To use Archives you must have Outlook 2007 or 2010 or use OWA. See this link: http://office.microsoft.com/en-us/outlook-help/license-requirements-for-personal-archive-and-retention-policies-HA102576659.aspx?redir=0
- As indicated above, Outlook 2003 does not allow for the use of all the features of Exchange 2010. This can be a pain if you are trying to update your clients in a phased approach.

just my thoughts. Hope it helps someone else.

Thanks,
CR

Your statement above concerning a CAS array requiring windows 2008 R2 enterprise is inaccurate. It only requires standard, even if you are using windows NLB.