Virtual machine provisioned and used space values appear higher in vCenter compared with the guest OS or VM Edit Settings

Products

• VMware vSAN

Issue/Introduction

Symptoms:

• Navigate to the vSAN cluster and select the Virtual Machine, note down the provisioned and used space.
  example : The provisioned space showing as 151.41 GB and the Used space showing as 135.46 GB
  
• The used space inside guest and on the edit settings of VM will show lesser than the values showing above. 
  Example : The provisioned space showing as 99.3 GB and the Used space showing as 32.2 GB
  

Environment

VMware vSAN 8.x
VMware vSAN 7.x
VMware vSAN 6.x

Cause

VM configured on the storage policy "raid5-erasure coding" policy with "Fault domain failures to tolerate" is set to 3". This is an expected behavior when the VM is configured with a storage policy that uses RAID-5 (Erasure Coding) with Failures to Tolerate (FTT) = 3.

Cause Validation:

• Navigate to Cluster > Configure > Fault Domains and verify that Fault domain failures to tolerate = 3
• Navigate to the affected VM and check the assigned policy under Configure > Policies. Confirm it is set to RAID-5 (Erasure Coding).
• Run the following command on an ESXi host to validate component usage:
  
  esxcli vsan debug object list --vm-name=VM_NAME
  

     Configuration:

        RAID_5
         Component: ########-####-####-####-############
           Component State: ACTIVE,  Address Space(B): 35791044608 (33.33GB),  Disk UUID: ########-####-####-####-############,  Disk Name: naa.################:2
           Votes: 2,  Capacity Used(B): 35966156800 (33.50GB),  Physical Capacity Used(B): 35609640960 (33.16GB),  Total 4K Blocks Used(B): 35569631232 (33.13GB),  Host Name: ############
         Component: ########-####-####-####-############
           Component State: ACTIVE,  Address Space(B): 35791044608 (33.33GB),  Disk UUID: ########-####-####-####-############,  Disk Name: naa.################:2
           Votes: 1,  Capacity Used(B): 35966156800 (33.50GB),  Physical Capacity Used(B): 35609640960 (33.16GB),  Total 4K Blocks Used(B): 35571912704 (33.13GB),  Host Name: ############
         Component: ########-####-####-####-############
           Component State: ACTIVE,  Address Space(B): 35792093184 (33.33GB),  Disk UUID: ########-####-####-####-############,  Disk Name: naa.################:2
           Votes: 1,  Capacity Used(B): 35961962496 (33.49GB),  Physical Capacity Used(B): 35605446656 (33.16GB),  Total 4K Blocks Used(B): 35575877632 (33.13GB),  Host Name: ############
         Component: ########-####-####-####-############
           Component State: ACTIVE,  Address Space(B): 35792093184 (33.33GB),  Disk UUID: ########-####-####-####-############,  Disk Name: naa.################:2
           Votes: 1,  Capacity Used(B): 35966156800 (33.50GB),  Physical Capacity Used(B): 35609640960 (33.16GB),  Total 4K Blocks Used(B): 35572916224 (33.13GB),  Host Name: ############

  Example output shows each component consuming ~33.50 GB. With four components, this aligns with the ~135 GB usage displayed in vCenter.

Resolution

This is expected behavior. No anomalies are present.

• The higher usage values in vCenter are due to the RAID-5 with FTT=3 policy, which increases storage consumption by design.
• In this configuration, the policy creates four components and and each disk holds full portion of the data in alignment with the erasure coding scheme and failure tolerance requirements.
• The provisioned space is also showing as expected. The calculation is as follows:
  Provisioned space = Hard disk size (100 GB × 1.33) + Memory (16 GB) = 149 GB, which approximately matches the 151 GB displayed in vCenter.”