Hyper-V Virtual Hard Disk (VHD) Performance White Paper

It must be white paper week 🙂 – today we posted a great document discussing virtual hard disk (VHD) performance with Windows Server 2008/Microsoft Hyper-V and Windows Server 2008 R2/Microsoft Hyper-V R2.  It’s about 35 pages long and goes into great detail on the test methodology as well as the results and application of the results…


Take a look:



Taylor Brown
Hyper-V Enterprise Deployment Team


Comments (7)

  1. aya2work says:

    Taylor, very interesting document, thank you!

    But can I ask one question? In document in section 6 in the table of VHD types compare I found such "cons" about dynamic VHD disks:

    "Defrag is not recommended due to inherent re-directional layer."

    But in document no any word about defag except this. Also, all what I read before about defrag VMs is "use it like real machines" – i.e. use defrag tools.

    Can you comment this more detailed? (or, may be, make a blog post about defrag of VMs (VHDs) (does we need it to do/how to/how often/what tools to use)

    ps: sorry for poor English.

  2. Alexander Bright says:

    Is there going to be any response to this. i´ts been more than two months.

  3. aya2work,

    Correct defrag is not recommended for dynamic or differencing disks – this is similar to the recommendation given for SAN LUN's utilizing thin provisioning or snapshots.  The rational for this is that running defrag can cause the size of the disk to grow as it moves bits around the ‘disk’ to what is preceded to be unused space thus causing us to back that space with actual disk space.


    Taylor Brown

  4. First time i read this documents its very informative for me. thanks taylor brown for this great effort.



  5. Hona says:

    This white paper with so called hard work and lot of performance comparisons turned out to be disappointment and useless document to me. I was looking for on official statement about the active active use of VHD or pass-through disks, and expected to see the information in the limitations section. Useless as it seems, microsoft will make all big comments about all the comparisons but will not mention about its limitations.

  6. Innocuous says:

    Good document. Thanks

  7. Innocuous says:

    Forgot to ask if there is a plan to update it to include factors specific to the capabilites of Hyper-V Server 2012?

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