Convert thick provisioned to thin provisioned using vmkfstools in ESXi Shell (command line)


Convert thick provisioned to thin with vmkfstools in ESXi Shell (command line)

In this step by step guide, you will learn how to convert a thick provisioned lazy zeroed disk to thin on VMware ESXi 6.7. The steps are the same for other ESXi versions. You will use the vmkfstools command.

The vmkfstools command offers the ability to clone virtual machine content and also convert from one virtual machine disk (.vmdk) format into another.

1. Check VM used space

The used space column shows the VM as 94.08 GB used space.

2. Confirm disk type by editing VM settings. 

Expand the Hard disk 1 and check the Type. The hard disk type is thick provisioned, lazily zeroed. ( default type) 
Note:  Shut down VM if you didn't do that already.( VM need to be in powered off state to do disk type change)

Step 2. Enable SSH on VMware ESXi host

Enable SSH via the GUI ( Web page) . Expand Host from left side and click on Manage. Click the tab Services and find the service name TSM-SSH. Click on Start.

Click refresh button to make sure service in running state. 

Step 3. Connect ESXi using SSH 

SSH into the host with the application Putty.( windows). if you are using linux or Mac OS use built in SSH command from terminal.

Putty Download url:

Click on "Accept" or "Connect Once"

Login with root account or other privileged account if you have LDAP or AD integration enabled. 

Step 4. Navigate to the VM folder

Navigate to the VM folder under /vmfs/volumes/ with the command cd /vmfs/volumes/<datastore name>/<VM name>.

Use ls-lh  command to list folder contents. 

Step 5. Convert VMDK to a thin provisioned disk using vmkfstools clone option.

command :    vmfstools -i <source vmdk> -d thin < destination VMDK> 

New VMDK and flat files are created under same directory

Step 6. Attach new Thin VMDK using GUI. 

Edit VM setting > Add hard disk >  Existing hard disk -- Browse the datastore select VM folder and select the thin VMDK

Note:  Ignore the Hard disk type displayed in the screen. By default it will show  Thick provisioned.  This will change to Thin once you apply settings. 

Step 7. Remove old ( Thick )  VMDK

Select or expand Old hard disk from Edit VM settings, Click on the cross ( delete) option at the right side. 

Check the delete files from datastore. Leave this unchecked if you don't want to delete the old disk now.  

Click Save. 

Step 8.Power ON VM

Step 9. Verify hard disk type conversion

Check the VM hard disk size. In this example, the hard disk changed from 94.08 GB to 9.95 GB. Also disk Type has changed to Thin Provisioned. 


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