Virtual Way

Following are the virtual disk types that are relevant to ESX/ESXi:

1. thin
2. pre-allocated (should be used instead of “thick” which we do not recommend any more)
3. eagerZeroedThick
4. rdm
5. rdmp

For the first 3 types of virtual disks, one should use the VirtualDiskFlatVer2BackingInfo as the backing for your VirtualDisk in the the VirtualMachineConfigSpec when creating/reconfiguring the VM.

* If the thinProvisioned property is set, it is a thin disk
* If thinProvisioned is false (or not set) AND eagerlyScrub is false (or not set), it is a preallocated disk
* If eagerlyScrub is true AND thinProvisioned is false, it is an eagerZeroedThick disk

For the last 2 types of virtual disks, one should use the
VirtualDiskRawDiskMappingVer1BackingInfo as part of the
VirtualMachineConfigSpec when creating/reconfiguring the VM.

* If the compatibilityMode property is set to virtualMode, the disk is of type rdm
* If it is set to physicalMode, the disk is of type rdmp