Can you re-allocate the resources (CPU and GPU) in a virtualization setup?

[schmunkel98]

Just watched this video again, and I am getting some conflicting answers in different forums. Can you shut down each VM individually and reallocate the resources (CPU cores and GPU's) to change from a solo user config to a 2 person(or more) config without reformatting? This would be the only way I would consider this type of setup as it allows scaling depending on how many people need to use it. For example, if only I was using the computer I could have all of the CPU cores and even multiple GPU's at my disposal. However, if a second user wanted to hop on, then I could allocate them CPU cores and a GPU. Hopefully this could be done without a reboot or complete reconfigure. Anyone tried this or know if all or part of this is possible?

[leadeater]

Short answer is yes, that is the benefit of virtualization. Even shorter answer is no don't do this.

 

Long answer is every time you need to make those types of changes you must shut down the VM, on top of this SLI/Crossfire does not work in an unRAID VM. If it were to work the most likely would be an AMD card that uses the PCI-E bus for Crossfire, I have already had this conversation with LimeTech/unRAID support.

 

I can't stress enough that you should not be doing this with the idea of being able to use 2 GPU's in a single VM. It barely makes viable sense when two people are going to be using the same system all the time.

 

I am a supporter of this type of idea but it comes with an EXTREME amount of buyer be ware and use at your own risk.

[schmunkel98]

This is still a hypothetical setup at this point, but I was curious about all of the limits of it. It is just a matter of it it is worth it to do something like this versus having 2 machines as you are only really saving on an extra case, PSU, and CPU without having the benefit of being able to use the second card when a 2nd user is not there. I would be curious to talk to anyone that is using this kind of a setup to see what they think after having it long term.

[leadeater]

10 minutes ago, schmunkel98 said:

This is still a hypothetical setup at this point, but I was curious about all of the limits of it. It is just a matter of it it is worth it to do something like this versus having 2 machines as you are only really saving on an extra case, PSU, and CPU without having the benefit of being able to use the second card when a 2nd user is not there. I would be curious to talk to anyone that is using this kind of a setup to see what they think after having it long term.

If you can't find anyone that has a dual GPU unRAID system to confirm SLI/Crossfire I might be able to do a temporary install and check it out, got two 290X's so in theory has a decent shot of working.

[schmunkel98]

I highly doubt I will find anyone as it has been hard enough to dig deep enough for good answers thus far. Don't blow anything up, but I would be curious to see your thoughts on that setup as you know more about this than anyone I have talked to so far.

[leadeater]

1 minute ago, schmunkel98 said:

I highly doubt I will find anyone as it has been hard enough to dig deep enough for good answers thus far. Don't blow anything up, but I would be curious to see your thoughts on that setup as you know more about this than anyone I have talked to so far.

Linus's video 2 Gamers 1 CPU is about the best guide you'll find on the matter. The only sticking point I can see is the use of the 2nd GPU when only 1 VM/person is using the system. It'll likely end up being idle and allocated to the 2nd VM.

 

Even with that downside 1 unused GPU is less of a cost than an entire system. The 2nd GPU doesn't even have to be as good say one model down from the primary as an example.

[schmunkel98]

4 minutes ago, leadeater said:

Linus's video 2 Gamers 1 CPU is about the best guide you'll find on the matter. The only sticking point I can see is the use of the 2nd GPU when only 1 VM/person is using the system. It'll likely end up being idle and allocated to the 2nd VM.

 

Even with that downside 1 unused GPU is less of a cost than an entire system. The 2nd GPU doesn't even have to be as good say one model down from the primary as an example.

So are you okay with the re-allocating of the CPU cores when 1 user is active versus 2, or is this a bad practice as well? I know the idea is to get a beefy CPU where missing even half the cores is still plenty for gaming.

[leadeater]

17 minutes ago, schmunkel98 said:

So are you okay with the re-allocating of the CPU cores when 1 user is active versus 2, or is this a bad practice as well? I know the idea is to get a beefy CPU where missing even half the cores is still plenty for gaming.

You will have to shut down both the VM you are taking them from and the one you are giving them to but sure it will work fine. Just don't install Windows with only 1 core else you can't add more, Windows installs different when 1 CPU/core vs multi cores.

 

It's not like the boot time of a VM is that long anyway and even less when using SSD.

 

One thing I would test is assigning all cores/threads to both VMs and let unRAID sort out the core usage/sharing, it is even less of a concern when the second VM is shut down. By default unRAID will balance the load across cores and depending on the game only 3/4 threads are used so on a 6 core CPU the games may not be sharing cores anyway.

[Electronics Wizardy]

On 5/23/2016 at 10:24 PM, schmunkel98 said:

Just watched this video again, and I am getting some conflicting answers in different forums. Can you shut down each VM individually and reallocate the resources (CPU cores and GPU's) to change from a solo user config to a 2 person(or more) config without reformatting? This would be the only way I would consider this type of setup as it allows scaling depending on how many people need to use it. For example, if only I was using the computer I could have all of the CPU cores and even multiple GPU's at my disposal. However, if a second user wanted to hop on, then I could allocate them CPU cores and a GPU. Hopefully this could be done without a reboot or complete reconfigure. Anyone tried this or know if all or part of this is possible?

You can assign your self all the cpu core and your coures will be slower when others are using them. 2 vms can use 1 core at the same time.

[Mikensan]

I'm not too familiar with linux kvm / unraid, but with vmware you easily over-assign the number of cores vs how many physical cores you really have. The time you run in to an issue is when say every system wants to peg the CPU at the same time. That's where "shares" come in so you can give certain computers priority over the others to balance it out. You could create two resource pools and assign the shares accordingly. However to use resource pools you need vcenter which is not free and complexity to the configuration :-P Maybe look for a similar feature on KVM, may need to edit the xml files of the VMs to configure these "shares" as I doubt unRaid gives you the ability via GUI.

 

https://pubs.vmware.com/vsphere-4-esx-vcenter/index.jsp?topic=/com.vmware.vsphere.resourcemanagement.doc_41/getting_started_with_resource_management/c_shares.html