Three types of virtual machine hard disk
- Thick provision Lazy Zeroed
- Thick provision Eager Zeroed
- Thin provision
Thick Provision Lazy Zeroed
- Creates a virtual disk in a default thick format.
- Space required for the virtual disk is allocated when the virtual disk is created.
- Data remaining on the physical device is not erased during creation, but is zeroed out on demand at a later time on first write from the virtual machine.
- Using the default flat virtual disk format does not zero out or eliminate the possibility of recovering deleted files or restoring old data that might be present on this allocated space.
- You cannot convert a flat disk to a thin disk.
Thick Provision Eager Zeroed
- A type of thick virtual disk that supports clustering features such as Fault Tolerance.
- Space required for the virtual disk is allocated at creation time.
- In contrast to the flat format, the data remaining on the physical device is zeroed out when the virtual disk is created.
- It might take much longer to create disks in this format than to create other types of disks.
- It provides on on-demand allocation of blocks of data.
- All the space allocated at the time of creation of virtual disk is not utilized on the hard disk, rather only the size with utilized data is locked and the size increases as the amount of data is increased on the disk.
- With thin provisioning, storage capacity utilization efficiency can be automatically driven up towards 100% with very little administrative overhead.