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I have a 4 cores/8 threads Intel Xeon processor. This is something I tried to particularly ask in SolusVM support, however I haven't got a good reply. I even don't know if they are right: they told me to, as I have 8 threads for 4 cores, opt for KVM for a great CPU sharing among VPS's. As I understood, they said OpenVZ won't support all the 8 threads (so that I can use my entire processor resources). But I know that OpenVZ is lightweight and, in most cases, works faster, so I have a preference for OpenVZ.

For my 4 cores but 8 threads CPU, which virtualization type would I need for setting up, with my Intel Xeon processor, about 30-40 VPS's per dedicated server? Both CPU and RAM must be shared among the VPS's.

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Which specific CPU model is this? – ewwhite Jun 3 '14 at 21:35
@ewwhite Hey! Intel Xeon E5-1620v2. – André Bazaglia Jun 3 '14 at 22:27
up vote 2 down vote accepted

OpenVZ and KVM are two very different products. KVM is virtualization, that creates a process that looks like a machine. OpenVZ is containerization, that runs under the same kernel as the host, and creates environment (containers with their filesytem, users, network interfaces) that are isolated one each other. Containers have less overhead, but are less secure then KVM. Choosing between KVM and OpenVZ should not depend on the CPU you have, but rather on what will be your workload, will it be for different companies or customers ...

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Yes, you are right about what you said when comparing OpenVZ and KVM. I was just worried about my CPU usage in OpenVZ: Linux recognizes the total threads as the total number of cores. So I do believe all CPU resources may be well shared among VPS's with OpenVZ. Am I right? – André Bazaglia Jun 4 '14 at 10:13
Yes you're right, OpenVZ from the kernel / hardware point of view is pretty much like if only one linux is running with several processes. It's the kernel's scheduler job to dispatch processes among cpu / cores / thread. – user801247 Jun 4 '14 at 14:31

As pointed above correctly, OpenVZ is not complete virtualization since each VPS does not have its own kernel. With KVM, each VM will have its own kernel and they very well isolated from other VM's on same host machine. Specific to your query of CPU allocation, we have seen KVM to be MUCH better at sharing the CPU resources and smartly monitoring it at all times. Hence, my vote will be for KVM.

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Hmmm really? I've been reading the opposite (OpenVZ using less CPU resources and running faster as it is lightweight compared with OpenVZ). But in your experience, you just said KVM to be better sharing CPU resources. Was it a notable difference when compared with OpenVZ? Please go on. I'm interested in the topic. :) – André Bazaglia Jun 4 '14 at 10:10
OpenVZ VM's does not have its own kernel in the VM's and hence the overhead is less (with quite a few limitations attached to it). KVM provides true virtualization where CPU resources can be shared more efficiently. – ruchir-softsys Jun 4 '14 at 11:44
Okay then, thank you so much! P.S: I would also mark your post as a correct answer but Server Fault just let me mark one. So, anyway, I appreciate your attention! ;) – André Bazaglia Jun 4 '14 at 15:27
Also, just to make sure I got your point: overhead in OpenVZ is less, but when you say KVM provides true virtualization, it means VPS's performance won't be affected by a possible abuser as the VPS hardware is more "isolated". It doesn't means, though, KVM will be able to take more advantage of CPU resources (which would allow me to create more VPS's without affecting server performance or using too much of total CPU when using KVM, for example). Right? – André Bazaglia Jun 4 '14 at 15:35
No problem! Glad that I could help! With regards to your queries: 1) There is high amount of isolation between KVM VM's and hence one VM will not be able to take control of entire host machine and affect other VM's (in case of CPU / RAM). 2) CPU resources are more evenly / effectively distributed in KVM and hence each VM will have better share of resources - but you may or may not be able to create more VM's depending on current usage of CPU on host machine. Overselling of CPU resources will have detrimental effect on performance in either cases. – ruchir-softsys Jun 5 '14 at 4:54

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