Thick-provisioned VMs on vSAN detected on vSAN-health check

Products

• VMware vSAN

Issue/Introduction

Impact/Risks:
If the VMs should be in "Thick provisioning", there will be higher vSAN datastore usage.

 

This health alarm is flagged because vSAN has detected thick-provisioned VMs even though the applied vSAN storage policy has object space reservation set to 0 (Thin-provisioned). It is recommended to reclaim the underlying storage from 'Thick' to 'Thin' which will improve storage utilization.

This health alarm will not check VMs deployed by ESX Agent Manager (EAM) as most of the VMs deployed as thick-provisioned by default or VMs with disabled tasks (vm.disabledMethod), for example, NSX Controllers.

Symptoms:

vSAN online health check reports warning for thick disks provisioned on virtual machines.

Below Alarm is reflected on the Cluster in vcenter UI.

Environment

VMware vSAN(All Versions)

Cause

This may be caused by the VMs being backed up from a SAN and restored to vSAN, regular storage vMotion shall always provision VMs with thin disks.

Resolution

If the VM should be using "Thick provisioning", please apply a Storage Policy to the VM with the vSAN option "Object space reservation" set to 100 (Thick provisioning).

If the VM should be using "Thin provisioning", see the workarounds below.

Workaround:

Option 1:

Apply a cloned vSAN policy that is Object space reservation 0%

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. Apply the Cloned policy to the VM that has the thick provisioned disks.
    

   a. Access the VM's configuration:
   Right-click on the VM in the vSphere Web Client navigator and select "Edit Settings"

   b. Navigate to VM Storage Policies:
   In the Edit Settings dialog, locate and select the "VM Storage Policies" tab

   c. Edit the storage policy:
   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
   
   d. Apply the changes:
   Click "OK" to save the changes and apply the new storage policy to the VM. 

3. 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. 
   
   
4. Reapply the <current policy> such as the "vSAN default polity" back to the VM. 

Option 2:

Schedule downtime for the VM and perform a clone within the vSAN datastore. The newly created destination VM should have thin VMDK(s). A back up is recommended as best practice.

It is recommend to perform a final check on the cloned VM and then delete the older respective VM from vSAN datastore, which should auto reclaim space upon deletion.

Option 3:

Perform a Storage vMotion of the VM onto a VMFS or NFS datastore as thin, then Storage vMotion it onto the vSAN datastore. See Migrating Virtual Machines with svmotion or more information.

Additional Information