Locating thin or thick provisioned disks
In the early version of ESXi, all VMDKs were thick provisioned disks, which means that all of the data sections of the disk were preallocated onto the backend storage. Thick provisioned disks can be inefficient, especially when there is a large amount of white space or unused space inside of the disk. For instance, if you have a 100 GB disk and only 21 GB is actually used by the guest operating system, you've lost 79 GB of usable disk space in your datastore that could be used by other virtual machines. As storage in vSphere evolved, and as virtualization matured, the concept of thin provisioned disks was introduced in vSphere.
Thin provisioning is the concept of allocating only the data sections of a disk that have data and not allocating any zeroed out sections of the disk. Thin provisioning can save a tremendous amount of backend storage since most virtual machines include some free space. Since the free space is not allocated, the use of thin disks...
