Can Zerto Exclude Disks or Volumes From Replication?

This is an article about Zerto, the award-winning IT Resilience platform I was first exposed to in 2011 and loved so much that I joined the team in 2012. For help with any Zerto-specific terminology, see Zerto’s official product documentation.

Note: this post refers to Zerto Virtual Replication versions 6.x and earlier.

A customer asked the following:

I am trying to figure out if Zerto can completely ignore certain disks on a protected VM. We have database backup dump devices that we do not want to replicate. I realize there is a Temp Disk flag that can be set that will not replicate changes after Initial Sync but, from the documentation I have found, Zerto still appears to require an Initial Sync of that disk.

Zerto doesn’t have a feature to completely ignore a disk or volume in versions 6.x and earlier. Note that doesn’t mean the feature is present in later versions, it strictly means I’m limiting myself to the context of versions 6.x and earlier!

This doesn’t mean the task is impossible. It does mean you must start with an empty source volume when protecting the virtual machine (VM) in Zerto. Sounds easy enough though, right? As some applications don’t appreciate having their temp data files destroyed, you should verify with the application owner and/or vendor before trying the workaround below. This process also assumes you are starting with a VM that is not protected by Zerto:

1. In the VM’s guest operating system (OS), follow the OS or application vendor’s process to empty the relevant volume of all data you wish to bypass from Initial Sync. This sometimes involves stopping any application from writing to the relevant volume and then deleting the files on the volume.
2. In the Zerto User Interface, Create or Edit a Zerto Virtual Protection Group (VPG).
3. Apply the configuration settings you intend to apply to the VPG but, at the Storage step of the Create/Edit VPG wizard, check the box labeled Temp Data for any/all relevant volumes:

   

4. Optionally, check the box labeled Thin if you wish to set the Recovery Volume to Thin Provisioned.
5. Continue to apply any configuration settings you intend to apply to the VPG, and then click Done.

If you created a new VPG, the VPG will next undergo an Initial Sync. If you edited an existing VPG, the VPG will instead undergo a Volume Initial Sync. Regardless of Sync type, while the relevant volume won’t be ignored completely, you may notice the Sync time is shorter as it has been reduced by whatever time it would have taken to sync that volume back when all the data was present. Note I say, “may” because it’s possible Zerto will read the entire source disk, as is the case when the source disk is thick-provisioned.

The result of all this? If you applied step 5, the result is no space wasted on temp/swap data that is generally useless in a recovery event.