How to Recover Failed Exchange 2016 DAG Member?

Summary: Exchange Database Availability Group member may fail due to various reasons, such as hardware failure, software issues, conflicting third-party applications, etc. In this post, we have explained the step-by-step process to recover failed Exchange 2016 DAG member. Also, we’ve mentioned an advanced Exchange recovery software that can help you recover mailboxes if the databases get damaged or corrupted.


How to Recover Failed Exchange 2016 DAG Member?

Although Database Availability Groups (DAG) provide a safe world for the admins and the business, they can have issues. Like other machines, they can also fail. The common reasons behind a failed Exchange 2016 DAG member are:

  • Hardware failure, a faulty motherboard, or other components in the server host or physical.
  • Software issues, caused by a conflicting or bad Windows update.
  • Third-party applications, which are not Exchange Server friendly, may lock important Exchange Server files.
  • Sudden loss of power and servers are rebooted without being properly shutdown. This could cause corruption in the databases or logs.
  • The server is infected with virus, malware, or ransomware.

Steps to Recover Failed Exchange 2016 DAG Member

Recovering failed Exchange DAG member isn’t just a re-install and re-join procedure. It involves a complete process to clean up the Active Directory/Exchange Server schema before installing a new member as a replacement. This is because most of the Exchange Server configuration is in the Active Directory Schema.

  • You need to first remove the failed member from the Database Availability Group (DAG). Use the following command to remove the database copies.

Get-MailboxDatabaseCopyStatus -Server <failedservername> | Remove-MailboxDatabaseCopy -Confirm:$False

MailboxDatabaseCopyStatus
  • Next, remove the server from the group by using the following command.

Remove-DatabaseAvailabilityGroupServer -Identity DAG01 -MailboxServer EX02 -ConfigurationOnly

DatabaseAvailabilityGroupServer
  • Now, you need to evict the failed server from the cluster. For this, use the command below.

Get-ClusterNode <failedservername> | Remove-ClusterNode

Get ClusterNode
  • Once this is done, you can go ahead and install the new server operating system or deploy the virtual machine. After installation is complete, you can go ahead and join it to the domain.
  • The next step is the installation of all updates, along with the confirmation of the current Exchange Server 2016 build and version installed in the cluster. You can get such information by running the Get-Exchangeserver command and checking the AdminDisplayVersion parameter.
Get-Exchangeserver
  • After you have joined the server to the domain, installed all updates, and confirmed the version and build of the current Exchange Server installation, you can go ahead and install the Exchange Server in the recovery mode. This is to install Exchange and recover all the configuration from the Active Directory Schema. Run the installation of Exchange with the setup /m:recoverserver command.

setup /m:recoverserver /iacceptexchangeserverlicenseterms

recover server
  • After the installation of the Exchange Server is complete, you need to add the server back to the Database Availability Group (DAG) by using the below command.

Add-DatabaseAvailabilityGroupServer -Identity DAG01 -MailboxServer EX02

  • Now the server has been re-joined to the cluster and DAG but there is no replication of the databases. So, if a failover occurs, Exchange Server will work but users will not be able to access their mailboxes, since these reside only on the other server. You need to add database copies to the newly restored server by using the following command:

Add-MailboxDatabaseCopy -Identity DBX01 -MailboxServer EX02

  • When this is done, it would be best to restart the Information Store service. At this stage, the database(s) added will start seeding to the newly restored server. Depending on the size and performance of the server and connectivity speed, it will take some time for the mailbox databases to be fully seeded. The changes will be replicated after the first seeding is complete. You can check the replication status by using the Get-MailboxDatabaseCopyStatus command. This will give you all the information about the data which is being synchronized between the servers.

Conclusion

The above steps will help you to recover failed Exchange 2016 DAG member. However, if there was any damage to the primary server mailbox databases and there might be corruption, then this could halt the replication of data. In such situations, you can use a third-party application, such as Stellar Repair for Exchange, to recover your data and service in the minimum downtime possible. Stellar Repair for Exchange can open any version of Exchange Server database and export the data to PST and other file formats. It can also export a recovered EDB file directly to a live Exchange Server database and Office 365 tenant. In case the live database is damaged and you cannot synchronize the database, you can easily create a new database and export from the damaged EDB file to the new database.

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