There are three disk types in vSphere.
Thick Provisioned Lazy Zeroes : every virtual disk is created by default in this disk format. Physical space is allocated to a VM when a virtual disk is created. It can’t be converted to a thin disk.
Thick Provision Eager Zeroes : this disk type is used in VMware Fault Tolerance. All required disk space is allocated to a VM at the time of creation. It takes more time to create a virtual disk compare to other disk formats.
Thin provision : It provides an on-demand allocation of disk space to a VM. When data size grows, the size of a disk will grow. Storage capacity utilization can be up to 100% with thin provisioning.
