Virtual disk provisioning is the process of managing storage space by allocating storage space on "as and when needed" basis. This simplifies storage administration by meeting capacity allocation on request. When creating a virtual disk for the virtual machine, there are three disk types available:
Thick Provision Lazy-Zeroed: When this option is selected, a virtual disk is created in a default thick format. If we create a 20 GB disk with this type, then 20 GB space is reserved for the virtual disk. However, the data on the physical device is not erased during the creation process; instead it is zeroed (erased) out on demand later during write operations on unused blocks inside the virtual machine.
Thick Provision Eager-Zeroed: When this option is selected, the complete space is allocated to the virtual disk during the time of creation. In contrast to Lazy-Zeroed, the data remaining on the physical device is zeroed out during the creation process...