VM used space showing higher values than consumed space on UI and/or GuestOS disk usage

Products

• VMware vSAN
• VMware Cloud on AWS
• VMware Cloud on Dell EMC

Issue/Introduction

Symptoms:
VM used space in vCenter UI may be bigger when comparing it to "Consumed Space" or "Disk used space" from GuestOS.

Environment

VMware vSAN 8.0.x
VMware vSAN 7.0.x
VMware vSAN 6.x

Cause

vCenter populates the UI with information about VM storage usage using different sources, this leads to a discrepancy when comparing the values from different perspectives (UI, VM view, Guest OS).

Resolution

vSAN engineering is aware of this cosmetic issue and is working on a fix for future releases.  For those using the VMC platform please file a Support Request, if the 'actual value' is needed as VMware Support will need to run the command to gather these details.

Workaround:

Starting from vSAN 8.0, a new data field was added to the output of the "esxcli vsan debug object list" command.
This new field is "Used 4K Blocks:" and it's the most accurate value when trying to identify how much a vSAN object is consuming, for example:

Object UUID: 7536ae61-####-####-####-########a9c
   Version: 15
   Health: healthy
   Owner: ###-10-###-244-1.eng.com
   Size: 1024.00 GB
   Used: 5.59 GB <----------------------------- old counter
   Used 4K Blocks: 1.35 GB <------------------- new counter, already showing a huge difference

 

The Cluster level vSAN usage information, found by following this path in vCenter "Cluster -> Monitor -> vSAN -> Capacity", has been confirmed to be showing the correct value. 

Additional Information

Impact/Risks:
This is a cosmetic issue, the used/consumed space discrepancy does not cause any impact to the environment or any of the vSAN functionalities.