required to the VM and can be shared between multiple VMs. Use DDA when you
need the full capacity and performance of the graphics card and its native drivers; for
example, when using CUDA cards for computational purposes or you need DirectX 12.
With DDA, you sacrifice density for application compatibility. Additionally, if you want
a Linux VM to have access to a GPU, DDA is the only option.
When you have a GPU-less environment, the WARP capability is used. This software
emulation of a GPU using a CPU is what we commonly see in most virtualization
environments. With the WARP driver, the graphical performance is low, but there is
basic DirectX support.
At the time of this writing, GPU partitioning is not supported by Hyper-V. GPU
partitioning works in a similar fashion to SR-IOV; a network adapter supplies multiple
“virtual functions” that act like network adapters that are then assigned to VMs, with
each VM getting a portion of the adapter’s resources. NVIDIA, AMD, and Intel are all
working on GPU partitioning technologies to expose their own versions of graphic
virtual functions, and I expect at some point in the future Hyper-V will support this.
The new graphical capabilities mean a lot more screen update data and therefore
bandwidth. The second original part of the RemoteFX technology package was a new
codec that was designed to efficiently encode and decode the display updates
associated with the more intensive RemoteFX-enabled workloads. This was the only
part of RemoteFX that was available to Remote Desktop Session Hosts in Windows
Server 2008 R2 before RemoteFX was more widely available in Windows Server 8.
The RemoteFX codec has been greatly enhanced since its original version. Consider a
typical highly graphically intense workload. In Windows 7, this workload may have
resulted in around 50Mbps of network traffic. With the Windows 8 changes, this same
workload resulted in around 5Mbps of traffic, which was reduced a further 50 percent
in Windows 8.1 to around 3Mbps of traffic. RDP 10 with Windows 10 and Windows
Server 2016 continues this evolution, as once again graphical remoting requirements
have changed, with 4K displays becoming far more common. RDP 10 introduces
H.264/AVC 4:4:4 mode support that results in less blurry text and better utilization of
hardware resources to improve the graphical fidelity and frame rates. This is required
because H.264 codecs are typically utilized, which are good for streaming video (such
as Netflix), and most graphics cards enable offloading of the processing; but this
results in the blurry text, which the AVC 4:4:4 mode codec fixes while still being able
to use hardware offloading. This is examined in detail at https://blogs.technet
.microsoft.com/enterprisemobility/2016/01/11/remote-desktop-protocol-rdp-10-avch-
264-improvements-in-windows-10-and-windows-server-2016-technical- preview/. The
4:4:4 is enabled by default for RemoteFX vGPU sessions but has to be enabled via
policy for all other sessions (DDA and WARP), and once enabled, all content uses
4:4:4 instead of the default Calista codec.
The final piece of the original RemoteFX technology is often overlooked; however, it
really completes the ability to have a fully featured remote desktop experience by
enabling the redirection of basically any USB device from the local client to the remote