Article number
Affected Versions

FTN-20210201: Zerto driver IO Inconsistency on ESXi 7.0 and 7.0 Update 1

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For vMware ESXi hosts on 7.0 and 7.0 Update 1, a rare issue may occur when a protected VM is hard reset or when a protected VM undergoes a vMotion operation. This issue results can result in inconsistencies in the replicated journal and long-term retention data. Upgrading to a recommended version will resolve the issue and perform a forced delta sync on all VPGs. For VPGs that are using long-term retention, users should take a new full copy. 

Target Audience

Users using ZVR versions 7.5, 8.0, and 8.5 with ESXi host versions 7.0 and 7.0 Update 1



In the versions noted below, Zerto has a rare software issue that can result in inconsistencies in the replicated journal and long-term retention data. This can only occur in the mentioned versions and when a protected VM is hard reset or when a protected VM is vMotioned in the environment. Due to this issue, Zerto has removed ESXi 7.0 and ESXi 7.0 update 1 from our interoperability matrix for the noted Zerto versions. 

In some cases, users will receive an alert that the VM cannot replicate because the protected disk is inaccessible. In other cases, users may not receive a notification that there is an issue with replication, but inconsistency may exist. This behavior only applies to the following ESXi and Zerto versions:  


  • VMware ESXi 7.0 and 7.0 Update 1 
  • Zerto 7.5 through 7.5 Update 4 
  • Zerto 8.0 through 8.0 Update 4 
  • Zerto 8.5 through 8.5 Update 1 


Please upgrade your Zerto Virtual Manager Sites to one of the versions noted below once available. During the upgrade, the system will automatically perform a “force sync" on all VPGs if there are ESXi 7.0 or 7.0 update 1 hosts in the environment. Users can optionally opt-out of this automated force sync in the installer during the upgrade, but this is not recommended unless they have a large environment. Users cannot disable this automatic force sync if upgrading via the silent installer, including MSP partners upgrading their customers via Cloud Control – Upgrade Manager. If users do not let the upgrade perform the force sync for them, the user must manually force sync all VPGs at this site as there could be an unknown inconsistency – this may be preferred for larger environments where more VPGs would need to undergo this force sync. For VPGs where long-term retention is configured, users should take a full copy to resolve these possible inconsistencies.  

When a VPG force syncs, this action will trigger a delta sync on the VPGs so that the protected and recovery volumes can be compared and synchronized. This sync is necessary to ensure that no disk-level inconsistencies between the protected and recovery disks are present. For VPGs that are using long-term retention, taking a full copy will ensure that that copy and future incremental data will not contain any inconsistencies. 

Please note that the fix for this issue will be made available for the following ZVR versions: 


  • 7.5U4p2 (ESXi 7.0 ONLY)
  • 8.0U4p1 
  • 8.5U2