vSAN witness reach 100% CPU Usage during hosts upgrade via vLCM

Products

• VMware vSAN 8.x

Issue/Introduction

During the ESXi hosts upgrade performed through vLCM, witness VM hit 100% CPU utilization and becomes unresponsive

Environment

VMware vSAN 8.x

Cause

While the host upgrade is in progress within the stretched cluster, a backup operation (LWD-snapshot) is triggered for the Witness VM as part of a scheduled backup task.

Resolution

Taking of snapshots on a vSAN Witness Appliance is considered a restricted practice and is not supported by VMware. Additional disk I/O overhead is introduced by this process, leading to a reduction in witness traffic speed and a negative impact on overall performance.

Additional Information

Additional Information: 
https://knowledge.broadcom.com/external/article/387069/avoid-taking-a-snapshot-of-the-vmware-vs.html

vLCM should not be used to patch the vSAN Witness Node itself.
https://knowledge.broadcom.com/external/article/399633/cant-patch-vsan-witness-host-vm-via-imag.html