Deciding On When To Use VHDX or VHD files with Hyper-V


As a follow up to yesterday's post, today's post is a quick run through of when and where you would choose VHDX versus VHD, based on some of the questions that have been asked at recent events.

Why would I still choose VHD files when VHDX files are a better option?

The main reason would be that you are exporting the virtual machine into an environment, tool or resource that doesn't require VHDX files. A good example of this is Azure's IaaS VMs, which still require VHD files. Note that if you are using Azure Site Recovery then replicating a VHDX is supported, but it will be converted automatically for you when needed.

What benefits does VHDX provide?

Larger virtual disks - up to 64TB instead of 2TB with VHD files
Better resiliency via protection against corruption during power outages by being able to log updates to the VHDX metadata structure
Alignment with 4K disks, which is pretty much what a typical disk is these days
Online resizing is also available with a VHDX file, but not available with VHD. This means you can grow or shrink the disk based on requirements without shutting down the VM.
Better performance, most notable during periods of disk expansion, which is one of the main reasons why people tend to adopt the VHDX format and migrate VHD files across to it.

What dependencies do Gen 1 or Gen 2 VMs have with the different virtual disk offerings?

Gen 1 VMs can use VHD or VHDX files, but Gen 2 VMs can only use VHDX files.

What are some of the other things I can do with a VHD or VHDX file?

You can use the Boot to VHD/VHDX feature, in which you can boot directly into a self contained operating system install that isn't running through a virtualisation layer, and they are also used if you want to use Microsoft's native iSCSI implementation in Windows Server 2012 R2. Being able to use volumes larger than 2TB here is obviously a huge benefit.

Can I convert a VHD to VHDX?

Yes, you can either do this through PowerShell, or through Hyper-V Manager


Can I convert a VHDX to VHD?

Yes, you use the same method as above, but just reverse the process.

When would I choose to continue working with existing and deploying new VHD files?

The main reason is for any workload that has a Gen 1 VM dependency, including certain Azure VM workloads at this point in time.

 

Comments (4)
  1. Andrew C says:

    The Wizard screenshot shown above looks exactly like what I am after. It’s a shame there is no mention of where this might be found (ie: it’s not in Hyper-V Manager on W7). Is this a Windows Server 2012 thing only?

    1. Hi Andrew

      This screenshot is from Windows Server 2012 R2, and I assume that Windows clients that support the Hyper-V role also have this functionality, which would explain why Windows 7 doesn’t have it because it still relied on Virtual PC.

  2. Sandra Diaz says:

    I use these step and successfully convert vhd into vhdx. but after conversion my vhd files get corrupted and i am not able to see my vhd files. I am listen about vhdx file viewer – freeviewer.org if any other way to open corrupted files

    1. Cain Ravenlock says:

      Try to run windows chkdsk or testdisk tool.
      If the scan is looping then your hdd probably have two MBR versions
      you can also choose in testdisk to copy MBR which will solve such a case.
      Many cases of seeming disk corruption are two different version of the disk exist.
      One is backup MBR and one is the main MBR if they dont have the same version the disk will become unreadable and all looks encrypted. (weird symbols as folder and file names)

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