Reducing VM storage consumption on VSAN datastore

Products

• VMware vSAN

Issue/Introduction

Symptoms:

VM's storage utilization on vSAN datastore shows higher than the actual usage.

Environment

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

Cause

Cause Validation:

VM configured on the storage policy "Stretched - Site Mirror" with "Raid-1, hostFailuresToTolerate: 1" policy with "Thick provision" Disks.

Policy:
  stripeWidth: 1
      cacheReservation: 0
      proportionalCapacity: 100    >>>>>>>>> (proportionalCapacity: 100 refers to Thick provision , proportionalCapacity: 0 regfers to Thin provision)
      hostFailuresToTolerate: 1    
      forceProvisioning: 0
      spbmProfileId: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
      spbmProfileGenerationNumber: 0
      replicaPreference: Performance   >>>>>>> ( Performance refers to Raid 1)
      iopsLimit: 0
      checksumDisabled: 0
      subFailuresToTolerate: 1
      CSN: xxxx
      SCSN: xxxx
      spbmProfileName: Stretched - Site Mirror
      locality: None

• "Stretched - Site Mirror" with "Raid-1, hostFailuresToTolerate: 1": This policy results in a 4x capacity consumption compared to the actual data usage, as it mirrors the data on other site.
• Thick provisioning is a type of storage pre-allocation. With thick provisioning, the complete amount of virtual disk storage capacity is pre-allocated on the physical storage when the virtual disk is created. A thick-provisioned virtual disk consumes all the space allocated to it in the datastore right from the start, so the space is unavailable for use by other virtual machines.

Resolution

• To reduce the storage usage, clone the same storage policy changing the disk provisioning type to thin provisioning and apply the cloned storage poly to VM.
                   OR
• Apply a suitable storage policy to VM which results in lesser capacity consumption compared to old policy "Stretched - Site Mirror" with "Raid-1, hostFailuresToTolerate: 1"

Additional Information

• Changing the storage policy may trigger a resync, which could impact performance. Therefore, it’s recommended to update the VM policy during off-business hours.
• Ensure VM disks are not running on Snapshots
• Verify that all disks are compliant with the current storage policy.