Convert a existing Virtual Disk on ESXi from Thick Provisioning to Thin Provisioning and vice versa

I was playing around on my ESXi server and noticed most of my servers were using under 10GB yet most where consuming between 20-45GB of datastore space. This is because when I set them up I went with the default setting of Thick Provisioning like many. So what do you do? I don’t want to reinstall my servers and loose everything. I also don’t want to waste space when I can afford new disks being unemployed at the moment.  After searching around I came across 2 nice articles on using vmkfstools to “convert” (it actually is cloning the disks) to Thin Provision and vice versa.
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