How to change the thick or thin provisioning of a virtual disk

First of all, we need to know the difference between thin and thick provision. The simplest explanation is that thin provisioning will consume only that much space that it needs initially and will grow based on the demand later. In contrast, the thick provisioning will consume the entire space from the datastore.

NOTE: Before changing from thin to thick and vice versa, please ensure a valid backup of the virtual machine and enough space.

To change vmdk from Thin to Thick provisioning

  1. Power off the virtual machine.
  2. Navigate to the datastore where the VM/ VM disk resides.
  1. Select the disk in question, and in the status bar above, you should find the Inflate option. The Inflate option converts the disk to thick provisioned.
  1. Once you’ve selected the inflate option, you should be seeing a task getting created for the vmdk inflation at the bottom in the Recent Tasks tab. This task usually takes some time to complete depending on the performance of the array. 
  2. After the inflation task is completed, if the VM in question is not reflecting the change, reload the .vmx file. For more information, see Reloading a vmx file without removing the virtual machine from inventory (1026043).

NOTE: If INFLATE button is grayed out, it indicates that the virtual machine is not powered off or that it is not thin provisioned.

NOTE: Please make sure there are no snapshots.

To change vmdk from Thick to Thin provisioning

NOTE: This process requires more than one datastore. If only a single datastore exists, you can clone the virtual machine to a destination machine with thin provisioned disks instead of migrating.

  1. Select VM you want to convert.
  2. Right-click the virtual machine and select Migrate.
  3. Select Change storage only and click Next.
  1. Select the option to configure per disk.
  1. Select the disk in question which needs to undergo the modification.
  2. Under the Storage, category select the destination datastore, and under the Disk Format option select Thin Provision.
  1. Validate the required VM Storage Policy and click Next.
  2. Review the information on the Review Selections page and click Finish.

Alternatively, virtual machine disks can be cloned to create new Thick or Thin provisioned VMDKs. For more information, see Cloning and converting virtual machine disks with vmkfstools (1028042 UP to VMware vSphere ESXi 6.7).

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