Eager/Lazy Zeroed

Posted on 2013-12-28
Last Modified: 2014-01-03
I would like someone to explain clearly what they mean by Eager Zeroed and Lazy Zeroed in Vmware vernacular.

if you back it up with an example it will be much helpful

Thank you
Question by:jskfan
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by:Tony Giangreco
Tony Giangreco earned 100 total points
ID: 39743481
Thick Provision Lazy Zeroed
Create a virtual disk in a default thick format. Space required for the virtual disk is allocated during creation. Any 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.

Thick Provision Eager Zeroed
Create a thick 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 during creation. It might take much longer to create disks in this format than to create other types of disks.
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by:Vaseem Mohammed
Vaseem Mohammed earned 100 total points
ID: 39743632
In Lazy zero blocks are reserved but not formatted/cleared for new data. As the data comes in, the blocks are zeroed and new data is written.

In Eager Zero, blocks are reserved and formatted/cleared and ready to write new data

That's the reason why it takes time for Eager Zeroed virtual disk type to be created than Lazy zeroed virtual disk.
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RickEpnet earned 100 total points
ID: 39743663
In theory the Eager Zero should be faster that Thin or Lazy Zero.  In practice the difference is not really noticeable. However unless you are pressed for time if you are going to use Thick I would use Eager. Why not pay the price upfront of writing to the blocks instead of having your application or OS pay the price while it is running.
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by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 200 total points
ID: 39743675
There are good articles written here by fellow vExpert Frank Denneman, which discusses Storage DRS, and time taken to Storage DRS (Storage vMotion) different disks types!

which came about from these articles discussed by other fellow vExpert Eric Sloof

I would give them all a read, because it's also now storage related, e.g. what type of SAN, and technology do you use.

Author Comment

ID: 39745216
***if the storage is brand new, no data in it…the lazy and eager zeroed still applies..??

*** is lazy/eager zeroed new term in vmware Vsphere or it has been used in the previous versions of Vmware ??
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Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 200 total points
ID: 39745287
***if the storage is brand new, no data in it…the lazy and eager zeroed still applies..??
- Yes, it based on the creation of the VMDK.

*** is lazy/eager zeroed new term in vmware Vsphere or it has been used in the previous versions of Vmware ??

These terms have been around for many years, in terms of VMDK format, but not always available from the GUI, or able to create the disks from scratch via a wizard!

Author Closing Comment

ID: 39748910
Thank you
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ID: 39754690
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