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What is the difference between a CPU and a vCPU?
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What is the difference between a CPU and a vCPU?

rchurchrchurch Member

Some VPSs quote a number of CPUs and others quote vCPUs?

How does the vCPU differ from the CPU? Do they refer to what a VPS is guaranteed,or what a VPS is guaranteed if they are available?

Do they have their CPU equivalents, eg Amazon mention in the past that a CPU was the equivalent of 1.7GHz Opteron or some other AMD CPU.

Comments

  • rds100rds100 Member

    a CPU is a real physical thing. vCPU is a marketing term used to describe part of a CPU (normally a core or a thread in the case of hyperthreaded CPUs).

    Thanked by 1lukesUbuntu
  • eddynetwebeddynetweb Member
    edited July 2014

    Generally, VPS hosts around here mean vCPUs. There are some (like AbusiveCores) that allocate a whole core to you, and you can use it around the clock. Besides that, most hosts enforce a shared policy.

    Allocation of threads/cores and such. :o

    Thanked by 1lukesUbuntu
  • AnthonySmithAnthonySmith Member, Patron Provider

    afaik no virt platform is capable of assigning a physical socket via pass through to a VPS, as such the host system allows the guest access to a core or number of cores, with or without pinning it is still essentially a virtual core in every instance so its just terminology, vCPU is the correct terminology, but in reality.... no difference.

  • Dedicated servers give you your own CPU with it's cores/threads allocated fully to you. Use away!

  • Most commonly 1/2 CPU = vCPU

  • DylanDylan Member
    edited July 2014

    @eddynetweb said:
    Generally, VPS hosts around here mean vCPUs. There are some (like AbusiveCores) that allocate a whole core to you, and you can use it around the clock. Besides that, most hosts enforce a shared policy.

    AbusiveCores doesn't really give you a whole core. You get a single thread (1/2 a physical core) on a hyper-threaded processor.

    Don't get me wrong, I'm not saying that's bad for what it is since maxing out a single thread is still more than most providers will let you do, but I do think the service's name is a tiny bit deceptive.

  • @Dylan said:
    Don't get me wrong, I'm not saying that's bad for what it is since maxing out a single thread is still more than most providers will let you do, but do I think the service's name is a tiny bit deceptive.

    Oh, I did not know that... Thanks for clearing that up. :-)

  • AnthonySmith said: vCPU is the correct terminology, but in reality.... no difference

    This. Some people say CPU, some say vCPU. At the end of the day, they are all "virtual" cores on a VPS.

  • wojonswojons Member

    @Dylan said:
    Don't get me wrong, I'm not saying that's bad for what it is since maxing out a single thread is still more than most providers will let you do, but I do think the service's name is a tiny bit deceptive.

    This is very true but its also a name it would then have to be absuive thread and that does not sound as good.

  • smansman Member
    edited July 2014

    vCPU is kind of meaningless with hyperthreading so yea it's more about marketing than anything else.

    You are not necessarily even getting 1/2 a core. Logically yes but hyperthreading isn't that good. If you don't believe me just look at pricing from dedicated server providers. If they do charge a premium for hyperthreading CPU vs non-hyper, it's usually minimal.

    The minimum # of vCPU's someone should get on a hyperthreaded CPU to give some idea what performance they could expect is 2. If it's only one then I think it will have a lot to do with what your neighbours are doing.

  • rds100rds100 Member

    Your neighbor always matter a lot, because the L3 cache of the whole CPU is shared. And a CPU without cache is worthless in terms of performance.

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