vSAN - Deduplication is not showing any space savings

Products

• VMware vSAN

Issue/Introduction

Symptoms:

• vSAN cluster with deduplication and compression enabled is seeing no result in the deduplication and compression overview.
• Summary tab screen reports that no space is being saved by deduplication and compression.
• You see low deduplication ratio.

Cause

This issue occurs because objects are 100% reserved.

Resolution

• Run this command on any of the hosts as it will display all disk information in the cluster:
  • esxcli vsan debug disk list.
  • The output from the command above is reporting all disks with high amount of reserved space.

 

• To fix this issue, ensure the storage policies are not set for object space reservation: 100% (Thick provisiong):
  • Click Menu > Policies and Profiles > Click VM Storage Policies > search for the vSAN Storage Policy or the custom policy used and select it, this will display the policy details and show it has 100% reservation:

Workaround:

• You can run this command on RVC to show disks stats as well and see object space reservation:
  • vsan.disks_stats <cluster>