Clarify some confusion on GPU pass-through?

[dirtyofries]

I have a spare video card laying around that I was thinking of dropping in my build.

 

 

Is there any value in having the card in there just for acceleration purposes under a VM accessed through RDP? I don't actually have a use for connecting a monitor and using the server as a direct desktop, but since so many apps (and Windows) can be GPU accelerated - does it help in this instance?

 

 

Is this even a thing?

[bungee91]

My question would be, what specifically do you want to run that uses the GPU for acceleration tasks?

I'd assume some form of transcoding, or something similar.

 

Considering that passing through a GPU can have a host of issues, I don't know that it is worth it (this comes from someone who regularly pass's 2 GPU's to VM's).

If the card is "friendly", then it should work well, however this definitely depends on the card.

What card would you be doing this with?

 

If you never plan to hook up a monitor to the GPU, you will have no way of seeing an output/boot up of the VM if for whatever reason it fails to boot.

This is because you need to remove the VNC section of the VM template once you pass though a physical card (as it causes issues, it is a one or the other kind of thing).

 

As for RDP, I wouldn't guess it would do much as you're not physically connecting to the card, however I am guessing at that.

 

I do know however that the displayed resolution with or without a card is different for me, however I believe that is when using TeamViewer, not RDP.

If I connect to a VM without a GPU, the resolution, and size is smaller than with one that has a GPU installed.

[jonp]

Short answer:  maybe.

 

Using a GPU would result in less overhead for the VM in general.  Without a physical GPU, QEMU has to emulate a graphics device that can provide a framebuffer.  There is definitely some overhead with that, but generally speaking, it's not a ton unless you're doing intense things inside the VM like video playback or if you're viewing it at a high resolution (e.g. 4k).  As bungee said, not all GPUs work well with GPU pass through.  That said, it's not too hard to try and see if it works, so I think what I would do is try out a VM without the GPU and see if it works well enough for your needs.  If it doesn't, try adding the GPU and see if that improves things.

[dirtyofries]

Hey, thanks to both of you - sorry I let the post languish.

 

 

To answer your questions - my purpose was to get video playback working more smoothly inside the VM, enable light video editing and speed up RDP.

 

 

I dropped in a fanless EVGA GeForce GT 720 and it works like a charm. There's a noticeable experience improvement on all fronts and the card barely gets warm.

 

 

The one drawback is there's no VNC if I need it, however I can always just swap the XML if it came to that.

 

 

Thanks for the great responses.

[jonp]

The one drawback is there's no VNC if I need it, however I can always just swap the XML if it came to that.

 

Why would you need VNC if you have RDP?  But yeah, changing the VM graphics from physical to virtual is fairly trivial.

[dirtyofries]

The one drawback is there's no VNC if I need it, however I can always just swap the XML if it came to that.

 

Why would you need VNC if you have RDP?  But yeah, changing the VM graphics from physical to virtual is fairly trivial.

 

 

Well, as far as I know RDC doesn't start until most Windows services have loaded, so if you're trying to watch the startup process, or start a safe mode session...things along those lines, you'd need VNC.

 

 

(Then again, I may be a total newb on all this).

[jonp]

The one drawback is there's no VNC if I need it, however I can always just swap the XML if it came to that.

 

Why would you need VNC if you have RDP?  But yeah, changing the VM graphics from physical to virtual is fairly trivial.

 

 

Well, as far as I know RDC doesn't start until most Windows services have loaded, so if you're trying to watch the startup process, or start a safe mode session...things along those lines, you'd need VNC.

 

 

(Then again, I may be a total newb on all this).

 

I gotcha, so for troubleshooting needs essentially.  Yes, you are right, you wouldn't get that using RDP.