Datacenter Switchover

A switchover is a manual process in which an administrator manually activates one or more mailbox database copies. Switchovers, which can occur at the database or server level, are typically performed as part of preparation for maintenance activities. Switchover management involves performing database or server switchovers as needed.

For example, if you need to perform maintenance on a Mailbox server in a DAG, you would first perform a server switchover so that the server didn’t host any active mailbox database copies.

There are four basic steps that you complete to perform a datacenter switchover, after making the initial decision to activate the second datacenter:

1. Terminate a partially running datacenter
2. Validate and confirm the prerequisites for the second datacenter
3. Activate the Mailbox servers
4. Activate the Client Access servers

Step by Step Exchange Datacenter Switchover

Make Sure Datacenter Activation mode for DAG is Dagonly

• Set-DatabaseAvailabilityGroup -Identity “DAG Name”  DatacenterActivationMode DagOnly

1. Terminate a partially running datacenter

If any DAG members in the failed datacenter are still running, they should be terminated.When the DAG is in DAC mode, the specific actions to terminate any surviving DAG members in the primary datacenter are as follows:

• DAG members in the primary datacenter must be marked as stopped

Turn off and Stop all Exchange Server Mailbox /CAS

• The second datacenter must now be updated to represent which primary datacenter servers are stopped.

  • Stop-DatabaseAvailbilityGroup “DAG Name”  –ActiveDirectorySite “Main AD SiteName” -ConfiguratonOnly

2. Validate and confirm the prerequisites for the second datacenter

• DNS in DR site reachable
• Domain controller reachable

3. Activate the Mailbox servers

• Cluster service must be stopped on each DAG member in the second datacenter

  • (Stop-Service ClusSv), or use (net stop clussvc)

• Force Start cluster service

  • net start clussvc /forcequorum

• Evict Primary Datacenter node

  • Failover Cluster Management tool -> cluster ->  Nodes -> More Actions -> Evict

• Mailbox servers in the standby datacenter are then activated by

  • Set-ADServerSettings –PreferredServer ‘DR Site DC”

  • Restore-DatabaseAvailabilityGroup -Identity “DAG Name” -ActiveDirectorySite“DR AD Site Name” -AlternateWitnessServer FQDN-DR -AlternateWitnessDirectory “DAGFileShareWitnesses-DR”

• Activate the Database in the DR site

  • Move-ActiveMailboxDatabase -Server “MBX-Main Site” -ActivateOnServer “MBX-DR Site” -MountDialOverride:None

  • Resume-MailboxDatabaseCopy -Identity “DB Name”

4. Activate the Client Access servers

• Change the CAS Array site

  • Get-ClientAccessArray -Identity mail | fl site #(Exchange 2010)

  • Set-ClientAccessArray -Identity mail(FQDN) -Site “DR AD Site Name” #(Exchange2010)

• Switch Exchange DNS To point to HUB/CAS server IP in DR site
  •   Mail.domain.com
  •           Autodiscover.domain.com

• Move OAB to the DR site
• Change the send connector source servers to DR server

Perform forest wide Active Directory Replication