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14 Dell EMC PowerVault ME4 Series and Microsoft Hyper-V | 3921-BP-WS
3.2.1 Convert VMs to a newer generation
Note the warning message in Figure 7 that the VM generation cannot be changed once a VM has been
created. However, it is now possible to convert a VM from generation 1 to generation 2. While Microsoft has
ongoing efforts to provide tools to perform this action, third-party tools are available (use at your own risk).
More information on this topic can be found on Microsoft TechNet.
3.3 Virtual hard disks
A virtual hard disk is a set of data blocks that is stored as a regular Windows file with a .vhd, .vhdx, or .vhds
extension, using the host operating system. It is important to understand the different format and type options
for virtual hard disks and how this integrates with ME4 Series arrays.
3.3.1 Virtual hard disk format
There are three kinds of virtual hard disk formats that are supported with either VM generation:
• VHD is supported with all Hyper-V versions and is limited to a maximum size of 2 TB. This is now
considered a legacy format (use VHDX instead for new VM deployments).
• VHDX is supported with Windows Server 2012 Hyper-V and newer. The VHDX format offers better
resiliency in the event of a power loss, better performance, and supports a maximum size of 64 TB.
VHD files can be converted to the VHDX format using tools such as Hyper-V Manager or PowerShell.
• VHDS (VHD Set) is supported on Windows Server 2016 Hyper-V and newer. VHDS is for virtual hard
disks that are shared by two or more guest VMs in support of highly-available (HA) guest VM
clustering configurations.
Virtual hard disk format options