vCenter server with thick provisioned disks on vSAN taking up space

Products

• VMware vCenter Server

Issue/Introduction

vCenter server upgraded/deployed using thick provisioned disks and deployment on vSAN, need to convert to thin provisioning to reclaim space. 

Example  

vSAN objects OSR attribute is set to thick for affected VM 

# esxcli vsan debug object list --vm-name=vm1 

Policy:
  stripeWidth: 1
      cacheReservation: 0
      proportionalCapacity: 100  <<< Object space reservation attribute is thick 
      hostFailuresToTolerate: 1
      forceProvisioning: 0
      spbmProfileId: aa6d5a82-1c88-45da-85d3-############
      spbmProfileGenerationNumber: 0
      CSN: 1007
      spbmProfileName: vSAN Default Storage Policy

Used:
  63753420800 <<< 63 GB usage
Size:
  1535450808320 <<< 1.5 TB provisioned space 
Type:
  vdisk
Path:
  /vmfs/volumes/vsan:52f4da6bda089860-eaf5############/f3ea5b68-f003-afd9-13ed-############/vm1.vmdk (Exists)

 

Environment

VMware vSAN (All Versions)

Cause

vCenter was deployed to the vSAN Cluster using "Thick Provision lazy Zero" disks during configuration.  A virtual disk configured as Thick Provisioned Lazy Zeroed forces vSAN to allocate 100% of its provisioned capacity immediately.

When a standard policy of Failure to Tolerate of 1 (FTT=1) is applied, the initial object layout requires 200% of the provisioned space to accommodate the "Thick Provision lazy Zero" disks.  So a 100GB VM would be 200GB on disk. 

 

 

 

Resolution

Convert the vCenter disks to thin provisioning using the below steps. 

1. Clone the current storage policy that is in use naming it <current policy>_clone.  
   Example "vSAN default policy" cloned to "vSAN default policy_clone"
   
   
2. Ensure that during cloned policy creation object space reservation attribute  is set to “Thin“ or Object space reservation 0
   
   
3. Apply the Cloned policy to the VM that has the thick provisioned disks.
   
   Right-click the VM and select VM Policies (or Edit Policies depending on your vCenter version) Click Edit VM Storage Policies.
   
   
4. There are 2 ways to apply the storage policy either to the entire VM or to individual disks.
   
   To apply the same policy to all disks: Select the desired policy from the dropdown list and click "Apply to All" 
   To configure policies for individual disks: Select the "Configure per disk" option and choose a different policy for each virtual disk.
   
   
5. Apply the changes:
   
   Click "OK" to save the changes and apply the new storage policy to the VM.
   
   
6. Validate that the Disks for the VM are no longer being reported as "Thick Provision lazy Zero" and are being reported as "Thin Provisioned" and that the space usage on the vSAN datastore has decreased.  This can take time depending on cluster performance and if Deduplication and compression are enabled. 
   
   
7. After confirmation on space reclamation, Reapply the <current policy> such as the "vSAN default polity" back to the VM. 

In vCenter web-client the VM should now report correctly per the vSAN policy in use.  If the VM is reporting the same used space and provisioned space in vCenter or there was no change, vMotion the VM to a new host to have it report in vCenter correctly. 

If further assistance is required open a case with vSAN Support.