Moving vSAN Host to maintenance mode takes long time

Products

• VMware vSAN

Issue/Introduction

Symptoms:

• The vSAN health displays alert on Disk Capacity usage, free disk space on a physical disk is above 80%.
  
  
• Object Rebalance/Resync In progress,
  
  

Environment

VMware vSAN 7.x
VMware vSAN 8.x

Cause

• When disk space utilization reaches 80%, vSAN tries to balance all the vSAN disks; this behavior is expected. 
• Resync is triggered on the cluster by this rebalance task.
• Because of this resync, it will take a long time if any host is placed in maintenance mode with "Ensure Accessibility" or "Full Data Migration."

Resolution

We must wait until the rebalancing is finished. After then, hosts may be put into maintenance mode.

Note: Rebalance activity may take longer time than expected, you can overcome wait times by taking the following actions. 

• Clean up space, look for VMs that are not in use or big files that can be deleted.
• Add more capacity disks to the hosts.
• Snapshot consolidation on VMs in use.