40842: Acronis vmProtect: Replication Takes More Time to Complete after Source VM Is Migrated to a Different Datastore

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Last update: Tue, 2013-08-27 13:32

Replication may take more time to complete if the original source VM has been migrated to a different datastore due to CBT tracking loss

This article applies to:

  • Acronis vmProtect


  1. You replicate a VM with Acronis vmProtect.
  2. The first initial replication takes for example 1 hour, while all subsequent (incremental) runs take 5-10 minutes.
  3. You perform Storage vMotion or migration of the source VM to different datastore.
  4. You run replication again and notice that even though the target replica location has not been changed (the replica VM is still there), the replication takes 1 hour, i.e. the same time as the initial first replication instead of 5-10 minutes usually required for incremental replication.


In some cases, such as a power failure or hard shutdown while virtual machines are powered on, CBT (changed block tracking) might reset and lose track of incremental changes. In vSphere 4.1 and prior, Cold Migration (but not Storage vMotion) could reset but not disable CBT. In vSphere 5.0 and 5.1, Storage vMotion will reset CBT. See VMware Knowledge Base: Changed Block Tracking (CBT) on virtual machines.

CBT utilization is the only method to perform incremental replication with Acronis vmProtect and thus loss of CBT leads to full initial replication attempt (long) instead of the incremental (short) one.


Avoid using storage vMotion/datastore migration of the replicated (source) VMs.

More information

While Storage vMotion/datastore migration affects replication performance, the host vMotion is unaffected. The original VM can be migrated between the ESX(i) hosts without the need to reconfigure replication (the fact of migration is automatically discovered by Acronis vmProtect).