Article number
Affected Versions
Source Hypervisor
Target Hypervisor

Problem with Slow Replication/Syncs Halting After Upgrade to Zerto 6.5

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After upgrading to Zerto version 6.5, an administrator may notice that overall replication and syncs are slow/stuck.

Root Cause

Bandwidth regulator is not allowing available bandwidth to distribute across VRAs correctly so some VRA replication/syncs are stalled.


VPGs will get stuck in a bitmap or delta sync.

VPGs that are not syncing actively may show higher than normal RPO figures.

Bandwidth Regulator logs on the Protected Site will show some VRAs have a "BwLim" of a very small number (in bytes per second):

VraBwLimit,server=<SERVER_GUID> host=<HOST_MOREF>,VraBwLim=206
VraBwLimit,server=<SERVER_GUID> host=<HOST_MOREF>,VraBwLim=3
VraBwLimit,server=<SERVER_GUID> host=<HOST_MOREF>,VraBwLim=500
VraBwLimit,server=<SERVER_GUID> host=<HOST_MOREF>,VraBwLim=1
VraBwLimit,server=<SERVER_GUID> host=<HOST_MOREF>,VraBwLim=1


To workaround this issue, disable Bandwidth Regulator entirely from the Site Settings menu in the Zerto GUI on the Protected Site.

This issue was permanently resolved in Zerto version 7.0.