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Linux virtualization + video workstation

mcljot

mcljot

mcljot

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4 Feb 2019
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Hi folks, I'm building a home machine to take some workload off my office machine (company owned) and allow me to work from home when I want.

I have a question about CPU vs. vCPU vs threads.

I need to run 8 - 10 VMs for OpenStack and OpenShift deployments (fewer if absolutely necessary). Initially I was speccing an i7 9700k, 8 cores 8 threads. How many CPUs/vCPUs does this give me to assign to VMs? I'm assuming 8, whereas the i9 9900k with 8 cores 16 threads would give me 16 vCPUs for my VMs? Or the i7 8700k with 6 cores 12 threads would give me 12 vCPUs?

I don't want to go Threadripper because I need to dual boot RHEL, and I want the ease of the Intel CPUs for compatibility. But maybe that's not correct?

For anybody interested, here's the plan so far:

Motherboard: Gigabyte Z390 Designare
CPU: i7 9700k or i9 9900k
CPU cooler: Noctua NH-D15
GPU: AMD Radeon RX580 8GB Pulse
Linux boot drive: Samsung 970 EVO 250GB M.2 NVMe
Mac OS boot drive: Samsung 970 EVO 250GB M.2 NVMe
Storage: Samsung 860 EVO 1TB SATA
Case: Phanteks Evolv X ATX

Cheers,
Alex
 
Last edited by a moderator:
The point of virtualisation is that you can over provision so that you can better optimise physical hardware usage. So you could run 10 VMs each with 4 vCPUs on an 8-core CPU. The VMs will just have to fight it out for the real resources (well the hypervisor will manage the load based on any priorities you have configured). RAM will most likely be the limiting factor before CPU; you haven't mentioned your RAM though.

You can reserve resources for a VM, but this is best avoided unless you have a good reason for doing this. Otherwise it can just lead to resources going unused even when there is demand from other VMs.

macOS can be hacked to run on AMD but it is more difficult and comes with limitations, so best avoided if possible. I actually run macOS VMs under VMware which can be done without any hacking of the macOS installation if running on Intel hardware. You don't get the graphics performance you get when running direct on the hardware but it is perfectly usable for testing and other light uses.
 
Hi, thanks for the response. RAM is 64GB of something, probably 3000MHz CL 15.

So, for example, with the i7 9700k I could assign 4 vCPUs to each of 10 VMs (total 40 vCPUs) while also running the host machine? How would this differ in performance from doing the same thing with an i9 9900k?

Much appreciated!
Alex
 
Whilst I said you could assign 4 vCPUs to each of the 10 VMs, I wouldn't necessarily recommend it. Normally you would just configure each VM to use 1 or 2 vCPUs. It all depends on what they are doing. Are they mostly sitting idle in a test/lab scenario? If so, then that would be fine. Do you really need to run all 10 at the same time? If you do and they are running demanding tasks then you probably need to be looking at a CPU with a higher core count. If each of your VMs is configured to use 4GB of RAM then that is obviously 40GB gone. Some VMs may need more than this depending on what they are doing.

The benefits of hyperthreading are very task dependent and maximum performance is only achieved in specific workloads. For VMware you would see 10-15% at best. I am not sure about other hypervisors.
 
Thanks, yes normally at the moment I'm assigning 2 vCPUs to each VM. Yes they generally sit idle. A typical test environment would be 3 OpenStack controller nodes (VMs), 1 compute node, and 3 storage nodes - total 7 VMs. I said 8 - 10 above to allow for a small OpenShift cluster, or a Red Hat Satellite server, or some other unforeseen requirement.

If the higher thread count of the i9 9900k isn't a concrete requirement for my application, I'm inclined to go with the i7 9700k.

This is a bit off-topic, but do you know if I can use the Samsung M.2 NVMe drive as a boot drive for the Mac OS without first having to install on a SATA drive and clone over onto the M.2? I'm reading conflicting reports on various forums.

Cheers
 
I don't think you will see any/much benefit from a 9900k from what you describe. I won't do any harm though, so if you have any spare budget...

I can't help with the macOS boot question. I now run mine as VMs and have never tried installing natively on an NVMe drive.
 
I can't add to this but just to make you aware that hackintosh is against the forum rules so I wouldn't discuss this on here.

Edit....
Any threads or posts in here discussing how to do anything that is against Apple's EULA will be removed and repeat offenders will be punished suitably.

These type of posts include:

  • Anything related to installing OS X on non Apple hardware (hackintosh)
  • Any discussion or suggestions regarding installing OS X on non Apple hardware (hackintosh)
  • Anything to do with installing OSX on non Apple hardware (hackintosh)
  • Basically anything whatsoever to do with building a hackintosh

Just don't even mention hackintoshing and you'll be fine.
Click to expand...

Taken from the apple section
 
Cheers ED209 and Journey! I reported myself :D ... so maybe this thread will just disappear. In the meantime, I have another off-topic question - how does one cool a reference Vega 56? Is that little built-in fan really enough??
 
Everything is here! Just waiting on the RAM now (should be here on Monday). I'm kind of disappointed I went for the big Noctua - I'm sure it will perform superbly, but the last couple of days I've really liked the clean and empty look of an all-in-one watercooler! Something like the Raijintek Orcus 280

40063606183_753939e6f9_b.jpg
 
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