zeroedthick (default) .
Space required for the virtual disk is allocated during creation. Any data remaining on the physical device is not erased during creation, but will be zeroed out at a later time during virtual machine read and write operations.
Space required for the virtual disk is allocated at creation time. Unlike with the zeroedthick format, the data remaining on the physical device is zeroed out during creation. Disks in this format might take much longer to create than other types of disks.
Space required for the virtual disk is allocated during creation. This type
of formatting doesn.t zero out any old data that might be present on this allocated space.
Thin-provisioned virtual disk. Unlike with the thick format, space required
for the virtual disk is not allocated during creation, but is supplied, zeroed out, on demand at a later time.