High CPU usage on ESXi host during vSAN resync

Products

• VMware vCenter Server

Issue/Introduction

• On vSAN cluster with Deduplication and Compression enabled, the vSAN host may show high utilization during resync operation.
• 'esxtop' command from the vSAN host will report 'Dedup-compTxn' and 'IORETRY Ingress' is consuming high CPU.

• 'esxcli vsan debug resync summary get' output from the vSAN host will show the resync IOPS are going to the host reporting high CPU usage.

Environment

VMware vSAN 7.x
VMware vSAN 8.x

Cause

vSAN resync is a resource-intensive operation. It requires CPU cycles for data processing.
During the large resync, when the IOPS are going to a specific host as part of rebalance or rebuild, the host will have higher CPU usage..

Resolution

Wait for the resync to complete. Once the resync is completed, the CPU usage will come down to normal.