This guide simply explains in a very easy way, all the technologies and procedures that you need to know to perform Exchange 2010 data center switch over, recovering DAG member or stretching DAG between sites.
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Restoring Services in the Primary Datacenter
- Power on the primary mailbox servers. If you open the cluster console on them, you can see that they reflect that they are evicted from cluster. Database copies on them are marked as Failed and there is no way to mount them on primary servers.
Verify that Cluster service on the DAG members in the primary datacenter have a startup type of DISABLED. If they do not, either the Stop-DatabaseAvailabilityGroup command was not successful or the DAG members in the primary datacenter failed to receive eviction notification after network connectivity between datacenters was restored. Do not proceed until Cluster service cleanup has occurred and Cluster service has a startup type of DISABLED. You can optionally run the following command on the DAG members in the primary datacenter to forcibly cleanup the outdated cluster information: “Cluster node /forcecleanup”
- Run the Start-DatabaseavailabiltyGroup –Identity DAG1 –ActiveDirectorySite NYC command on them.
Note that powering those servers in the primary site will not be risky as they are out of DAG configuration. The start-DatabaseAvailabilityGroup command will return them to the DAG again.
Also remember that we have performed the Move-ActiveMailboxDatabase command during switchover to be servers in the secondary site. That’s why when you start-DatabaseAvailabilityGroup on primary servers, they will notice that the databases are active on secondary mailbox servers and will not try to do anything.
After running this Start command, the primary mailbox servers will start appearing in the cluster console as cluster nodes functioning normally.
- Run Set-DatabaseAvailabilityGroup cmd without any parameter to make sure the right Quorum mode is being used. This command also will seed all changes on the passive copies.
- Database copies on the primary site will start seeding automatically and will turn healthy eventually.
- Leave the database to replicate over time and sync from Secondary datacenter to Primary. Then proceed to the below steps.
- Note that the DAG is using the alternative witness server. In order to use a witness server in the primary site, and if you still have the old witness server, then use Set-DatabaseAvailabilityGroup -Identity DAG1 command. If we want to assign new witness on the primary datacenter, then add the witness parameters to the previous command.
- Notice that the default cluster group is hosted on the secondary site which means that the Primary Active Manager PAM is located on the node who holds the default cluster group.
To identify the PAM server, run: Get-DatabaseAvailabiliyGroup –Identity DAG1 –Status |FL *Primary*
- You can move the default cluster group to the primary mailbox server by running Cluster group “Cluster Group” /MoveTo:EX01.
- Dismount databases in the secondary datacenters and move the CAS URLs.
- After DNS is replicated and the cache is refreshed, use the Move-ActiveMailboxDatabase for the copies in the primary site.
- Mount database copies in the primary site.
- Outlook clients will find a message to indicate that the administrator has changed something and the outlook need to be restarted.
Note : When mounting database copies on the primary site, sometimes you will face issues like database cannot mount because index problem. For this scenario, you can run :
Update-MailboxDatabaseCopy DBName\FailedToMountServer –CatalogOnly
If this didn’t work, use:
Move-ActiveMailboxDatabase “Database Name” -ActivateOnServer DestinataionServer SkipClientExperienceChecks
Note that this command is powerful, look at this :
Move-ActiveMailboxDatabase “Database Name” –ActivateOnServer –Options