What Is The Difference Between Eager Zero And Lazy Zero Thick Provision Disks?

[Devalreddy]

When we allocate disks in VMware, we have to specify thin provisioned,  thick provisioned eager zero or thick provisioned lazy zero, but what is  the difference?

[nielse]

This is taken from the documentation:

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.
Thin Provision	Use  this format to save storage space. For the thin disk, you provision as  much datastore space as the disk would require based on the value that  you enter for the disk size. However, the thin disk starts small and at  first, uses only as much datastore space as the disk  needs for its  initial operations.

More information: http://pubs.vmware.com/vsphere-50/index.jsp?topic=%2Fcom.vmware.vsphere.vm_admin.doc_50%2FGUID-4C0F4D73-82F2-4B81-8AA7-1DD752A8A5AC.html

[aquila72]

On what occasions do you use one rather than the other?

[TomHowarth]

you would provision eager zero'd when you need fast write performance.  perhaps for a DB or an Exchange DAG.  personally I have not used them all that much as the time laying them out is quite long and it is very intensive on your Shared storage.

[umanmd707]

Hi - I guess by now you understand the basic definitions of these different Virtual Disk Provisioning Policies through articles like vSphere Documentation Center

However, would suggest you to check this Eager thick vs Lazy thick disk performance | Rickard Nobel to understand these disk provisioning policies in detail that would probably help you more.

Regards.

[Alex_Romeo]

Hi,

Thin provision: is when the disk is created but the size of the disk is equal to the size of the content. Lower write performance.

Thick provision lazy zeroed: the disk created has the same size as the storage on the storage, but the blocks inside are initialized immediately before being written. Average performance.

Thick provision eager zeroed: the disk has the same dimensions as the ones that are set but the blocks inside are cleared at the time of creation, so the performance will be better.

Alessandro Romeo