Replication, Backup or Both?

Q: If I use replication for a virtual machine does that mean that I no longer need to worry about backing it up?

A: The short answer is you should still back up the virtual machine! The reason is that all data protection systems seek to eliminate the two critical challenges of downtime, and data loss. Each problem costs the business lots of money. In the IT industry the goals of limiting, or even eliminating, data loss and down time are referred to as Recovery Point Objectives (RPO) (for data loss), and Recovery Time Objectives (RTO) (for downtime.) Replication makes a copy of a running virtual machine and then synchronizes updates from that running VM at regular intervals so that the replica is ready to run with the most current information should the need arise for a failover. The content of a replica changes with each new synchronization. Failover can take place very rapidly and often results in little to no downtime for the business and a very low RTO.

A Veeam Backup makes a point in time archive of all the files, settings, snapshots, binaries, and configuration files that make up a VM. This archive is stored in a single file (*.VBK) that is often compressed and deduplicated to save disk space. Completed backup files give the business a point in time from which to recover any and all files associated with a VM. If backups are completed with regular frequency they can be very effective at preventing data loss entirely and at recovering data in the event of accidental or purposeful deletion. Backup provides a very strong RPO solution.

There are those who might wish to argue that a good replica could also reduce RPO while also reducing RTO, however because the replica, which is actually a functional set of a virtual machine’s files, is constantly changing with synchronization updates there is never an established point in time from which to initiate recovery. In addition it is important to note that during failover a replica VM is locked to changes and a snapshot is used to enable VM operation while preserving the original state of the virtual machine.

The long and short of it is really pretty simple. Replication is a great way to get reduced RTO. Backup is still the best way to reduce RPO. Use both!

For more information about all things Hyper-V in Windows Server 2012 please check out the free E-book from Veeam “The Hands-On Guide to Understanding Hyper-V in Windows Server 2012.”