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A virtual machine that Azure Site Recovery helps protect goes into a resynchronization state

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This article fixes an issue in which a protected virtual machine (VM) that use Microsoft Azure Site Recovery (ASR) goes into a resynchronization state repeatedly.

Original product version:   Microsoft System Center 2012 R2 Virtual Machine Manager
Original KB number:   3094171

Symptoms

A virtual machine (VM) that Microsoft Azure Site Recovery (ASR) helps protect in a Hyper-V to Azure scenario may repeatedly go into a resynchronization state. You cannot manually resynchronize, and you may receive the following error message for the replication health of the VM:

Replication State: Resynchronization required
Replication Mode: Primary
Current Replica Server: Microsoft Azure
Replication Health: Critical
Resynchronization is required for the machine X. Resume replication to start resynchronization.
Successful replication cycles: 0 out of Y (0%). More than 20% of replication cycles have been missed for virtual machine X.

Note

In the error message, the placeholder X represents the name of the VM, and the placeholder Y represents the number of attempts.

Cause

This issue can occur if the data disk size of the protected VM is greater than or equal to 1 terabyte (TB).

Resolution

The maximum disk size that is supported for data disks in Azure is currently 1 TB. To work around this issue, reduce the hard disk to less than 1 TB. For more information, see the following article:

Protecting large data disks using Azure Site Recovery