Restoring DR Site in Exchange 2010 SP3 and then switching back to primary Site once primary site is up

My LAB Setup:
  •      SITE-A: Primary AD Site, 2 MBX Node
  •      SITE-B: DR AD Site, 1 MBX Node
  •      DAG Name: DAG01
So to replicate the disaster, I shut down both of the mailbox servers in SITE-A, now my Cluster has gone Down.

And DBs are dismounted and no copy is active at this time.

So to restore the services, I need to restore the DAG in Site-B.
First I need to stop the DAG in Site-A using the below cmd.

Stop-DatabaseAvailabilityGroup DAG01 –ActiveDirectorySite SITE-A

This will evict both nodes in Site-A from the Cluster.

Next, to restore the DAG in SITE-B, I will be running the below CMD.
Restore-DatabaseAvailabilityGroup DAG01 –activeDiretorySite SITE-B

This will use the alternate FSW preconfigured at the time of the setup to restore the functionality of the DAG.

Now you can check the DAG status and it will show the Nodes from the SITE-A are showing in StoppedMailboxServers.

Note: The other way to bring the Cluster up manually is the force start the cluster and then evict the node manually from cluster manager and then change the Quorum Configuration to Node and File Share Majority.

Now if you check the status of the DB and copies, you will see that DB on the DR node are now mounted.

You have Restored the DR Site successfully, users may expect the below notification, and would require restarting of the outlook clients, mobile devices using active sync may reload the mailbox.

Note: This post was limited to restore mailbox role only, in the case of disaster you may require to perform additional steps as well to restore the Client connectivity, SMTP Relay etc, depending on your setup.
Now to restore the Primary Site once the SITE-A has been brought back.
Run the below CMD.
Restore-DatabaseAvailabilityGroup DAG01 –activeDiretorySite SITE-A
This will Join back the node in SITE-A back to Cluster
And you can see the Cluster Configuration has switched back to Node Majority
Now move the PAM to the primary Site using the below CMD.
Move-ClusterGroup -Cluster DAG01 -Node SITEA-MBX1 -Name "Cluster Group"
Note: you will have to import the failover cluster module for the same, I have explained the whole process here.

Next, redistribute the Databases copies, and we are all set.