How many Cores should I assign?

[rl2664]

Hello everyone,

 

I have only one Windows 10 VM up and running and now I asked me, how many of the four cores my i5 have should I assign to the VM? Three cores for the VM and leave one for unraid or is it possible to assign all four Cores to the VM that the VM and unraid share all Cores?

 

Greetings

Ronny

[SSD]

The conventional wisdom is to leave one core (lowest core) for unRaid. This was based on some evidence that unRaid could "starve" if all CPUs were passed through. (You can use the low core for emulator for VM.)

 

But I'm not sure people have tried passing through all cores recently. KVM has continued to be worked on, and the problem may be resolved. You could certainly experiment passing through the all cores and see if you have problems.

 

A quick search found this where a user said they passed all 4 cores to one VM and 2 to another VM and didn't have issues.

 

https://forum.level1techs.com/t/kvm-and-pass-through-questions/122025/9

[1812]

I've passed through all cores with little to no issues. The main thing to do is make sure that your vm core 0 is not the same as the single core you've dedicated to unRaid. Many os's like to run those during boot and for some single thread os operations, causing a potential stall when both unRaid and the vm OS put a heavy demand on it. If unRaid is only managing vm's and not running dockers or anything else on the single core, it should pose no problems (at least in my experience.)

[ashman70]

What are you using the VM for? If you aren't using for anything CPU intensive, then start with one core, if you find that's not enough, add a second.

[rl2664]

Ok thanks, I tried all four cores, and it worked without problems.
At the moment the VM has not much load because I backup my NAS box to the unraid server with the VM. Fiddling around with rsync scripts is a nightmare for me. Dsynchronize is way easier to handle for me.
I will also try the other way. Stepping down to two or only one core to figure out what is really needed. I only want to be sure that I don't kill my unraid system by assigning all Cores to the VM...

[SSD]

17 hours ago, rl2664 said:

Ok thanks, I tried all four cores, and it worked without problems.

 

Running all cores has always worked initially. You won't know if this is a stable configuration until you give it some time and it may require load in unRaid and in the VM.

 

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