Azure Hybrid & Cloud Migration Blog

Building Exchange Server Disaster Recovery and Site Resilient setup requires proper planning and choosing the right option to select the underlying infrastructure. Recently I came across one Exchange DR solution architecting where customer was replicating its primary Exchange Server DAG LUNs to its secondary or DR EMC VNX SAN using EMC RecoverPoint. At this point of time customer didn’t had Exchange Servers installed in the secondary / DR Datacenter. Now when customer started planning phase to build the Exchange disaster recovery and site resilient setup in its secondary datacenter then, they started looking into various option of replicating Exchange Mailbox Databases to DR Exchange Servers.

Since customer was using EMC RecoverPoint for replicating all its data and primary SAN LUNs to DR storage, they first preferred to use the same underlying infrastructure. EMC RecoverPoint provides data loss by keeping replicated data in the journals and restore of the replicated data in any point in time back. In addition to this it also does data compression and data dedup. With this entire feature EMC RecoverPoint saves a lot of network bandwidth for WAN connection between two sites.

Now the question is can we use EMC RecoverPoint to replicate Exchange Mailbox Databases for setting up Exchange Disaster Recovery and Site Resilient setup?

According to EMC documentation (Exchange 2010 Disaster Recovery options with Cross-site Exchange DAG and EMC RecoverPoint) they provide two possible options, where in the first option they highlight few of the shortcomings of Exchange DAG native replication over EMC RecoverPoint, and in the second option they want you to use EMC RecoverPoint instead of Exchange DAG native replication.

So which option shall we select for Exchange Mailbox Database replication? To answer this question let’s see the below bullet points:
EMC RecoverPoint Replication:

• According to above provided EMC documentation link,  EMC provides option to setup Exchange Cold DR, where one has to keep its DR Exchange Servers shutdown and primary SAN/RecoverPoint will keep replicating the Exchange Mailbox LUNs to the DR SAN.
• This is going to be your Exchange COLD DR means it’s not straight forward there are possibility that you might see unknown issues while recovering from disaster.
• In this option upon perform Exchange DR drill or trying to activate Exchange Server from the DR there penalty of steps need to be carry out in order to bring the databases up. These steps might include creating new Exchange Databases on DR Exchange instances and re-homing user mailboxes.
• This Exchange cold DR setup with EMC RecoverPoint would require you to have more administrative overhead by attaching the LUNs to the node, ensuing that correct LUNs order and their drive letters are in use, and etc…
• There are always possibilities that during Exchange DR drills or datacenter failover you might run into split-brain syndrome, because there is no method available to check if databases are being mounted in both the datacenters during or after recovering from the disaster or drill.
• Not supported by Microsoft.

Microsoft Exchange DAG Native Replication:

• Going with Exchange DAG native replication option over EMC RecoverPoint is an absolute wise choice because you will be using Exchange Database Availability Group and all other associated Exchange Disaster Recovery and Site Resilient components such as DAC, Log shipping and log replay which ensures that your Exchange DR Mailbox database and services are healthy.
• Choosing Exchange DAG option would allow you to get support from Microsoft in case any thing breaks in the middle while going to EMC cold Exchange DR Option will not be supported.
• Less possibility of data corruption.
• One of the bad side of Exchange DAG replication is that it would ask for little bit more WAN network bandwidth.
• More control on Exchange DR drills and data integrity, where mounting one database from the Exchange DR servers and performing the data integrity while having everything running from the primary datacenter. Flexibility is available with Exchange DAG.

To conclude this it is recommended that one should choose Exchange DAG native replication over any other sort of appliance based technology for replicating Exchange mailbox database LUNs data. Exchange DAG provides proper safety against data corruption and split brain scenarios.

I will further update this article soon with more facts and reasons to share with you guys.

Cheers!