Figure 11.11 shows the filesystem objects related to my collection. You can see the
copy of the actual reference virtual machine and its storage and then folders for each
of the virtual machines. Notice the size of the VHDX files. The VHDX file in the IMGS
subfolder is the original VHDX file that was exported from the reference virtual
machine, so it has the same original size, 12GB. For each of the virtual machines, VDI-
0 and VDI-1, there are two virtual hard disk files. The first is the VDI-n.VHDX file,
which is the original virtual machine checkpoint state, RDV_Rollback, and then there
is an AVHDX file, which is the current state of the virtual machine that has the
differences from the checkpoint state. (This is normal.)
Figure 11.11 The deployed VDI collection filesystem content for the virtual hard disks
But why is the main VHDX file for each virtual machine only just under 2GB in size
compared to the 12GB of the main image? The answer is that the RDS VDI collection
is being efficient with storage and creates differencing disks for each virtual machine
in the VDI collection instead of a complete copy of the original image. This can be
seen using the Get-VHD PowerShell cmdlet on one of the VM instance VHDX files, as
shown here:
PS C:> Get‐VHD .\VDI‐0.VHDX
ComputerName : SAVDALHV91
Path : c:\clusterstorage\vms\vdi\vdicollection\vdi-
0\virtual hard disks\vdi-0.vhdx
VhdFormat : VHDX
VhdType : Differencing
FileSize : 1881145344
Size : 64424509440
MinimumSize : 64423477760
LogicalSectorSize : 512
PhysicalSectorSize : 4096
BlockSize : 2097152
ParentPath : C:\ClusterStorage\VMs\VDI\VDICollection\IMGS__1–
336FD568–1D1D487\VIRTUAL HARD DISKS\WIN10ETEMPLATE.VHDX