Q. What are VHD Sets in Windows Server 2016?
A. Windows Server 2012 R2 introduced shared VHDX which allows VHDX files stored on Cluster Shared Volumes (CSV) and connected to the SCSI controller to be shared between VMs and viewed as shared SAS. Configuring a disk as shared is enabled via the advanced features of the disk when connected to the SCSI controller with Windows Server 2012 R2 however this changes in Windows Server 2016.
In Windows Server 2016 a new type of VHD is available, a VHD Set which is a VHD created with a VHDS extension. The actual VHDS file is only 260KB but an AVHDX file is also created which stores the actual data and this can be dynamic or fixed. AVHDX is often used with checkpoints but does have more uses as the AVHDX is an automatic VHDX file used in various scenarios.
When creating with Hyper-V Manager the new VHD Set is a disk format option along with VHD and VHDX. When creating with PowerShell just specifying a vhds extension automatically sets it as a VHD Set.