[VMC on AWS] Unable to snapshot a VM, with error: A digest operation has failed.

Products

• VMware Cloud on AWS

Issue/Introduction

This document is meant to help customers understand and resolve issues with CBRC-enabled VMs migrated to VMC.

Symptoms:
This issue affects any VM which is, or was cloned from, a Horizon-deployed VM that was migrated to the SDDC.

When attempting to create a snapshot on a workload VM inside a VMC-on-AWS SDDC, the task fails with this error:

Operation failed!
Task name = Create virtual machine snapshot
Target = VM_name
Status = An error occurred while taking a snapshot: A digest operation has failed.

If you search for "cbrc_filter" in LogInsight, the failure matches with errors in vmkernel.log:

2021-01-26T12:00:10.287Z esx-2.sddc-x-x-x-x.vmwarevmc.com vmkwarning: cpu8:10371125)WARNING: VSCSIFilter: 345: Couldn't add filter 'cbrc_filter' to VSCSI_Handle 0x4313a24e5f40 (ID=0x20ac): Unknown VSCSI filter
2021-01-26T12:00:10.287Z esx-2.sddc-x-x-x-x.vmwarevmc.com vmkwarning: cpu8:10371125)WARNING: VSCSI: vm 10371115: 4142: Attaching filter 'cbrc_filter' on scsi0:0 failed: Not found (195887107)

Cause

As indicated in the Horizon on VMware Cloud on AWS Support KB, CBRC is disabled by default in VMC environments and cannot be enabled. From version 8, Horizon automatically disables CBRC for VMs deployed to VMC on AWS pools, but VMs deployed in CBRC-capable environments that are migrated to a VMC SDDC need to have CBRC manually removed, before or after migration, in order to be fully functional.

Resolution

To remove CBRC from the VM, power it down, then delete the .digest files in the VM folder for the affected workload, and from the Datastore Browser download its .vmx file. Edit the .vmx file to remove lines referring to CBRC such as:

scsi0:0.digest = "TRUE"

For each of the VM's virtual disks, delete the corresponding digest line if it is present, then save the .vmx file. Upload this .vmx file back to the VM folder on the SDDC storage volume, overwriting the previous version of the file.

Note:  While edit the VMX, VM should be power-off and post editing reload the VMX to action. 

Verify that you can now successfully create a snapshot of the VM and power it back on.