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Cannot boot a converted Gen 2 VM RRS feed

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    I converted a VMWare Workstation 14 VM to Hyper-V (vhdx). Although I can boot and use it in a Gen 1 Hyper-V VM, I cannot get it to work in a Gen 2 VM.

    My understanding is booting to a SCSI disk is not possible via Hyper-V, when although this worked in VMWare. I am then limited to booting a Gen 1 VM using IDE controllers. In a nutshell...is there going to be a performance hit here? Would I recognize any performance lagging compared to using this same vdisk in a VMWare-based VM?

    In research, someone created a Gen 1/Gen 2 conversion script 5-6 years ago...a) will it still work with today's tech/software, b) is it necessary to do a conversion?

    Basic VM characteristics...

    2 processors
    4GB RAM
    45GB disk
    Wednesday, June 26, 2019 7:03 PM

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    Hi ,

    How did you convert these VMs? Did you use disk2VHD? As far as I know, some third-party V2V converter will create generation 1 VM by default.

    Please first check if the following link is helpful:

    Disk2VHD on a Generation 2 VM results in an unbootable VHDX

    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    There are lots of threads talking about the issues caused by conversion. If possible, I would suggest you build new VMs on Hyper-V and migrate the data.

    >>is there going to be a performance hit here? 

    Generation 2 VM is hypervisor aware, and does not rely on synthetic or emulated hardware. For this reason, Generation 2 VMs often offer improved performance, such as faster boot times, than Generation 1 VMs.

    Best Regards,

    Candy





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    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   


    Thursday, June 27, 2019 2:52 AM

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    Hi ,

    How did you convert these VMs? Did you use disk2VHD? As far as I know, some third-party V2V converter will create generation 1 VM by default.

    Please first check if the following link is helpful:

    Disk2VHD on a Generation 2 VM results in an unbootable VHDX

    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    There are lots of threads talking about the issues caused by conversion. If possible, I would suggest you build new VMs on Hyper-V and migrate the data.

    >>is there going to be a performance hit here? 

    Generation 2 VM is hypervisor aware, and does not rely on synthetic or emulated hardware. For this reason, Generation 2 VMs often offer improved performance, such as faster boot times, than Generation 1 VMs.

    Best Regards,

    Candy





    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   


    Thursday, June 27, 2019 2:52 AM
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    I converted a VMWare Workstation 14 VM to Hyper-V (vhdx). Although I can boot and use it in a Gen 1 Hyper-V VM, I cannot get it to work in a Gen 2 VM.

    Once it becomes a BIOS-mode Hyper-V VM, you must make some deep changes to the contained Windows installation in order to switch to UEFI-mode boot. This is normal.

    My understanding is booting to a SCSI disk is not possible via Hyper-V, when although this worked in VMWare. I am then limited to booting a Gen 1 VM using IDE controllers.

    Hyper-V has fundamental differences from VMware's products, especially when it comes to emulated vs. synthetic hardware. Gen 1 VMs cannot load the necessary SCSI driver prior to starting up due to their BIOS architecture. Gen 2 VMs can, as a result of their UEFI architecture.

    In a nutshell...is there going to be a performance hit here? Would I recognize any performance lagging compared to using this same vdisk in a VMWare-based VM?

    I have read some unvalidated reports of performance degradation in high-duress uses. It's doubtful that you will see any difference. At most, a Gen 2 VM starts a little faster.

    In research, someone created a Gen 1/Gen 2 conversion script 5-6 years ago...a) will it still work with today's tech/software, b) is it necessary to do a conversion?

    The necessary modification to switch from BIOS to UEFI boot mode has not changed, so the utility should still work. I personally have not tested it recently, though. Due diligence says to take a backup before trying it anyway, so no harm in making the effort.

    Eric Siron
    Altaro Hyper-V Blog
    I am an independent contributor, not an Altaro employee. I accept all responsibility for the content of my posts. You accept all responsibility for any actions that you take based on the content of my posts.

    Thursday, June 27, 2019 2:12 PM
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    Hi ,

    Just want to confirm the current situations.

    Please feel free to let us know if you need further assistance.                   

    Best Regards,

    Candy

    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   

    Monday, July 1, 2019 3:18 AM
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    Hi ,

    Did you have any updates on this issue?

    Best Regards,

    Candy

    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com   

    Wednesday, July 3, 2019 6:52 AM