Datacenter switchover for exchange 2010

Henrik Walther explains the difference between the two in his article below. It will be beneficial to read the whole 13 part series. It is pretty close the your scenario with four MBX servers in a DAG ( 2 at primary and 2 at DR).

http://www.msexchange.org/articles-tutorials/exchange-server-2010/management-administration/planning-deploying-testing-exchange-2010-site-resilient-solution-sized-medium-organization-part9.html

Normally, in the case of datacenter, you typically go for (manual) switchover as it is not recommended nor is it wise to let a(n) (automatic) failover occur.

Hope that helps

i have drafted few steps but not sure. Could you please confirm the correct as it is very critical for me to draft them correct.

1) Move FSW to DR site.
2) Mount all databases in DR site.
3) change active preferance 1for DB  to DR Site.
4) Stop-DatabaseAvailabilityGroup –Identity <DAGName> -ActiveDirectorySite <primary site> -ConfigurationOnly:$True [Repeat for any additional Active Directory sites that are not the recovery datacenter.]

5)Stop-DatabaseAvailabilityGroup –Identity <DAGName> -MailboxServer <DAG member in primary site> -ConfigurationOnly:$True

6)Get-DatabaseAvailabilityGroup –Identity <DAGName> | FL
7)Stop the Cluster service on each DAG member in the recovery datacenter.  To do this run the appropriate command for your DAG member’s operating system:
Windows Server 2008 R2:             Stop-Service Clussvc

8)Restore-DatabaseAvailabilityGroup –Identity <DAGName> -ActiveDirectorySite <recovery site> 

9)
Get-ClusterNode –Cluster <DAGName>
Get-ClusterGroup –Cluster <DAGName>

10>change DNS entry and point to DR site CAS server.

I assuming that you have to site primary and secondary, primary site DAG members are EX1,EX2 and secondary site/DR site DAG members are EX3 and EX4. Your primary Datacenter DAG members and domain controllers are up, so The very first thing we need to do is to make sure the DAG member servers in the primary datacenter (EX1 and EX2 MBX Servers) are marked as stopped in the DAG.

1. Stop-DatabaseAvailbilityGroup DAGEXNH –ActiveDirectorySite DC1
where DAGEXNH is the dag name and DC1 is the (AD) site name for the primary site.


To confirm you need to run the following:
2.  Get-DatabaseAvailabilityGroup DAGEXNH | fl Name,StoppedMailboxServers,StartedMailboxServers

The next thing you must do is to stop the cluster service on each DAG member server in the failover datacenter, run the following command on each DAG member in the FO DC:
3. Stop-Service ClusSvc

After this you have to run the abovementioned, you need to restore the DAG by running:
4. Restore-DatabaseAvailabilityGroup DAGEXNH –ActiveDirectorySite DC2
where DAGEXNH is the dag name and DC2 is the (AD) site name for the failover/secondary site.
The mailbox databases will now activate on DR server EX3 assuming the database copies on this server has a lower activation preference set than EX4.

5. Pointing DNS Records to the CAS Array in the Secondary/Failover Datacenter


you don't need to do 1,2,3. Alternate FSW is already mentioned and becomes active when you run restore-databaseavailabilitygroup cmdlet. You DBs also become active on DR DAG members. No need to change preference as EX1 and EX2 are not considered during restore-databaseavailabilitygroup cmdlet as they are inactive. Your step 4, come into play if all Exchange Servers(MBX,CAS/HUB) and domain controllers in the primary site are unavailable (Actual Disaster). In which case only your first step change with -configurationonly:$true being added.