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  • 1.  VM provisioning

    Posted Jul 18, 2012 01:05 PM

    Hi techies,

    Still i am not so clear about Thick Disk Egar Zerod and Lazy Zerod,  What senarios we will use These options, can some one make me understand. Thanks in advance.

  • 2.  RE: VM provisioning

    Posted Jul 18, 2012 01:21 PM

    Here is VMware blog explaining it in very detail

    Quick Definitions:

    Eager Thick: Creates VMDK's, allocates and zeros all the blocks. - Best write speed

    Lazy Zero: Creates VMDK's allocates all the blocks but doesnt punch any zeros. Best use of disk space.

  • 3.  RE: VM provisioning

    Posted Jul 18, 2012 03:08 PM

    Thick Disk Egar Zerod - used for FT, microsoft cluster, oracle cluster

    with the eager zero, during the vmdk creation itself the entire space is zero filled in the vmfs filesystem. so whenever a vm writes data there is no need to do the zeroing, with the lazy zero when ever a vm writes first that portion of vmdk needs to be zero filled and then it writes the actual data, there you loose some write performance.

    Lazy Zerod- general use, you can use..

  • 4.  RE: VM provisioning

    Posted Jul 18, 2012 03:34 PM

    Choice of hiring a lazy guy doing just in time work saving you space and money OR hiring a anxious guy who proactive work however

    costing more money and filling space early.

  • 5.  RE: VM provisioning

    Posted Jul 18, 2012 03:30 PM


    I find a good way to think about this is that it shares some similarities to Windows Disk Formatting in that:-

    Lazy Zero is equal to a quick format.  All the space is allocated straight away but only the initial blocks are zeroed.  This gives you access to the space quickly but write performance takes a hit as vmware will need to zero the blocks as they come to be used.

    Eager Zero is like a full format.  Again all the space is allocated straight away but vSphere goes across all the disk and zeroes all allocated blocks.  This means it can take longer for the disk to be available for use but write performance will be improved as all the blocks have been pre-zeroed.

    Hope this helps,


  • 6.  RE: VM provisioning

    Posted Jul 18, 2012 03:38 PM

    Just to confirm is this for Thick Eager Zero and Thick Lazy Zero?  If so the space is allocated straight away regardless of zero type.  Only with Thin Provisioning is the space not pre-allocated.



  • 7.  RE: VM provisioning
    Best Answer

    Posted Jul 18, 2012 05:26 PM

    for both eager and lazy the space will be consumed from the VMFS, but the entire zeroing will happen only in the eager type and on demand zeroing will occur in the lazy type

    hope this clears the confusion

  • 8.  RE: VM provisioning

    Posted Jul 19, 2012 11:14 AM

    Thanks a lot guys, it's really helped me to understand.

  • 9.  RE: VM provisioning