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OpenVZ vs KVM and Xen
standardlook
Member
in Help
I understand those in terms of providers being able to oversell. You can theoretically oversell more on an OpenVZ than KVM, and more on a KVM than Xen. However, do all KVM and Xen VPS providers allow complete dedicated usage of the data? I have yet to see one host let OpenVZ for dedicated but have seen quite a few allow clients to use as many allotted resources (i.e. CPU) on a KVM. Is that just a coincidence or do all KVM VPSes have dedicated resources?
Comments
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Aside from resources:
OpenVZ: You can't use your own kernel & have to bear host node's kernel.
KVM & XEN: You are able tobuse your own kernel so that you can install Windows, CoreOS etc on containers.
Docker will not work on most of OVZ
That opinion incompetent you can sold as many as want CPUs and all swap on KVM node can be sold as ram
For example 12 HT cores 64 GB RAM 64GB Swap Node can be easily sold as 60, 1 cores 2GB VMs but customers wont be very happy
and also KVM support burstable memory and on some panels and inside a virtual machine it shows burstable top amount... or on 1GB -2GB burst KVM you will see 2GB but if you can use it depends...
So it is about the provider and how much did you trust him and how low is the price
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Actually first it is about how much did you trust your provider, then it become problem of sustainability... if a provider do not profit on his offers it's eventually (with high probability) go to the dead pool )
So a provider can achieve higher density with Containers than with VMs without quality drops significantly... which mean more as income for it or can be interpreted as better sustainability on lower prices... or can also mean more bang for the buck... it all depends of the provider, experience, knowing what they doing and eventually trust that they do what they promise, not just blindly sold unbelivable offers....
Chart came from Praralles (and is a bit of advetisment) but that is from official expo and is said infront of audience ... test is on simple Xenon system, VM / Container that runs webserver is started and webserver is hammered with requests, then process is repeated until webserver response time go over 4 seconds and results are:
That data can be interpreted in several ways... from that if you has to choose vz vs kvm from a provider point of view eventually to acheive same level of sustainability on kvm node price need to will be double... or if the price is same eventualy node will be twice as slow / twice as loaded... and some other variations i depend on provider and trust/price
OP, Don't listen to @BharatB on this one
Thin provisioning and virtio_balloon allows KVM to be oversold on disk and memory, and as said above by @coolice you can oversell cores, and bandwidth.
So the biggest difference is you can run your own kernel and set kernel mods like a real (virtual) server, which you can not do with openVZ and XEN-PV unless the provider allows, which varies from provider to provider.
EDIT: I was typing while @coolice made the post above. He stated the situation very well.
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but will not stop ultra cheap provider from overselling ... that's the point ....it as easily as in vz and only not experienced enough provider will sell swap directly how i sed it leads to unhappy customers
Swap will be used to allow overselling, then if control panel shows only maximum memory amount you can play with that and adjust right memory shares 1GB minimum -2GB maximum most customers will not notice if memory shares is adjusted smart ...
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@BharatB Thanks, My point is that if customer do not trust that provider will deliver what is promised than virtualization technology choice won't stop it not to....
@standardlook are you wanting to know this stuff to be a provider, like @BharatB is talking about, or as a customer looking to make a good buying choice, like @coolice is saying ? Obviously it makes a difference which side of the fence you are on.
OpenVZ does NOT use Paravirtualization. It uses Container like virtualization (like a chroot but separated processes and networking)
Xen uses Para or HVM.
Holy shit, how do you even get 1st line support work....
Don't mind but he didn't ask anything he can do or not. He just want to know the changes so tell him valid differences else CTRL+F4 is your friend.
I am looking at it from a customer point of view.
OpenVZ - It lets you do everything which you can do with a KVM except the kernel & custom OS. It is cheaper because it has less overhead, takes less resources to boot & can be oversold more easily. It does not support Windows officially.Abusive neighbors can easily impact performance of your OpenVZ VPS.
KVM - An isolated environment just like a dedicated server which lets you install your desired kernel & OS e.g Windows. It also supports ISO installations. It is expensive because it has more overheard & takes more resources to boot. It can also be oversold but not as easily as OpenVZ. Abusive neighbours will make less of an impact on your KVM VPS.
Which one to go with - Depends on your requirements & personal preference. However if the applications you want to run don't require custom kernel, you can easily go with OpenVZ as you won't notice any significant difference between them.
Choose a provider which is knowledgeable & has enough technical skills to manage his nodes. An OpenVZ with a good provider can outperform a KVM from a bad provider easily. Similarly a KVM from a good provider can outperform an OpenVZ from a bad provider easily. So performance depends on number of factors mainly the knowledge & approach of your host.