VCPU is the other half of hyperthreading/smt Rhe route I have gone is a used cpu board combination there are tons of them on ebay and they are a single epyc but combined less than 300. And the core density is amazing.
The again. NEW AMD Epyc 7551 32-Core 64-Thread 2.0GHz CPU Retail Box NO VENDOR Lock for 99 bux. That's worth it. On Thu, Jul 20, 2023, 5:17 PM Ryan Petris via PLUG-discuss < plug-discuss@lists.phxlinux.org> wrote: > That's right, a vCPU is a shared resource. > > Lets say that you had a machine with 4 cores on it. To the operating > system, other than some nuances with the cache, PCI connections, etc., each > core is effectively its own CPU, and therefore we'll say the machine has a > total of 4 CPUs. Now, just becuase it has 4 CPUs doesn't mean that you can > only run 4 programs at a time; you can run hundreds or thousands of > programs at the time time, and the operating system will schedule those to > run on the CPUs. Each program will get some CPU time, more so if other > processes aren't doing much. > > Now, think of each vCPU as a process running on the host machine. The host > machine will time share those vCPUs across the actual CPUs just like any > other process running on the machine. But, within the virtual environment, > it is seen as a real CPU to the guest operating system, and it will > schedule programs to run on that CPU accordingly. > > So, you effectively have two layers of scheduling happening. > > There's not necessarily a limit on the number of vCPUs, just as there's > not necessarily a limit on the number of processes that you can run. Yes > there are technical limits on the number of processes that can be run, but > that's an operating system limitation. > > Now, you can assign a vCPU to have exclusive use of a CPU on the host > system, however unless you have some critical application where that's an > absolute must, it's really not necessary; you're just slowing down every > other process on that machine as they're no longer able to use that CPU > when nothing else is using it. > > Now, if your machine is super busy and you have virtual machines competing > for time, then you have what's called "steal time" or "CPU Steal", which is > the amount of time a vCPU waits for control of a real CPU; you can read > about that here: > https://blog.appsignal.com/2021/09/15/cpu-steal-time-a-crucial-metric-for-cloud-servers-and-vms.html. > But if that becomes a problem, you're overloading your system and it > doesn't really matter how many threads your host system has. > > On Thu, Jul 20, 2023, at 12:59 PM, techli...@phpcoderusa.com wrote: > > On 2023-07-20 10:55, Ryan Petris wrote: > > The CPU's cheap because it's old and no one wants them anymore -- it's > > of the same generation as 6000 series intel processors (i.e. skylake). > > It also uses a server socket, so the only motherboards you're going to > > be able to find are server motherboards. Those are going to be > > expensive and/or have other quirks, such as requiring a vendor > > specific heatsink, or a vendor-specific power supply, or take 5 > > minutes to start up, etc. > > > > You'd be better off spending money on a last-gen cpu and motherboard, > > for instance here's a combination that is relatively cheap: > > > > $174 for an i5-12400, which according to cpubenchmark.net is nearly > > 30% faster than the Xeon you linked (score of 19501 vs 15146, much > > faster single-core score as well): > > > https://www.amazon.com/Intel-i5-12400-Desktop-Processor-Cache/dp/B09NMPD8V2/ > > > > $139 for a compatible motherboard: > > https://www.amazon.com/GIGABYTE-B760M-DS3H-AX-Motherboard/dp/B0BSP61QZC/ > > > > I also wouldn't pay so much attention to the number of "threads" you > > think you'll need; you can run many VMs with a total number of virtual > > processors that is much more than what you actually have, and as long > > as you're not trying to go whole hog on every machine at the same time > > you'll be fine, and even if you do, you'll still be better off with a > > faster processor with a few fewer threads than an older slower cpu > > with more. > > --- > > Several months ago I did some research on what a vCPU is. I could not > find an exact answer. What I came away thinking was a vCPU is equal to > a thread. From what you are saying it sounds like a vCPU is a shared > resource, so there may be more vCPUs than actual threads? Is there a > way I can determine the number of vCPUs a CPU will provide? > > > --- > > > > > On Thu, Jul 20, 2023, at 10:26 AM, Keith Smith via PLUG-discuss wrote: > > > >> Hi, > >> > >> I was surfing the Inter Web when I happened upon a Xeon server CPU. > >> It > >> > >> is marked at $32.49 at Newegg. It has 12 cores and 24 threads and > >> has a > >> > >> good benchmark score. > >> > >> > > > https://www.cpubenchmark.net/cpu.php?cpu=Intel+Xeon+Silver+4116+%40+2.10GHz&id=3179 > >> > >> https://www.newegg.com/p/274-000A-007K2?Description=Xeon > >> > >> In the future at some point I would like to build something with 20 > >> plus > >> > >> or minus cores and 40 threads more or less for Proxmox. This would > >> be > >> > >> over kills because I only need 1 or 2 VMs active at one time... > >> maybe 3 > >> > >> in an extreme situation. > >> > >> This 12 core/24 thread CPU with 64Gb of Ram and a 1Tb SSD would > >> really > >> > >> be more resources than I would ever need. Off the top of my head > >> this > >> > >> means I might be able to build a decent Proxmox server for $500 - > >> $600. > >> > >> I do not need fancy video except for one VM that might be running > >> Win 10 > >> > >> or 11... I assume a server grade CPU would handle Win 10 and 11? > >> > >> Am I on the right track? > >> > >> Thank You For Your Feedback!! > >> > >> Keith > >> > >> --------------------------------------------------- > >> > >> PLUG-discuss mailing list: PLUG-discuss@lists.phxlinux.org > >> > >> To subscribe, unsubscribe, or to change your mail settings: > >> > >> https://lists.phxlinux.org/mailman/listinfo/plug-discuss > > > --------------------------------------------------- > PLUG-discuss mailing list: PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > https://lists.phxlinux.org/mailman/listinfo/plug-discuss >
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