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Why do people pay more for KVM or XEN?
I can't understand why people want KVM or XEN better than OpenVZ for Linux server.
I think there aren't many people who really need KVM or XEN over OpenVZ.
The only strong point of KVM and XEN over OpenVZ I know is more isolation.
But do you really need more isolation?
From my personal experience, when people on same node abuses, your vps gets slower no matter if it is KVM or OpenVZ.
Also, most providers load commonly used modules such as tap/tun and netfilter/iptables for OpenVZ.
AFAIK, OpenVZ has way much better performance than any other virtualization methods.
As long as provider does not oversell (and that is the reason why I stick to famous providers such as buyvm or hostigation), OpenVZ seems to be the best virtualization method for common uses of server.
There was one exception in my case when I wanted to use OpenCV library and needed to load special module for better image processing.
But except for those special cases, I can't get why people love KVM or XEN so much.
I believe there should be good reason that I don't know yet.
Could someone tell me why?
Comments
They think they're getting a premium product, and are willing to pay more for it. Which is fine, because i'm willing to charge more for it. I like money.
The most common rationale I seem to read is that people believe that it's harder for providers to oversell KVM or Xen. Effectively, they're throwing money at performance. Whether or not they actually get it would be a lively discussion.
This is LowEndTalk. I hope people have good reason for what they are paying.
People still have that overselling argument with OpenVZ but in my eyes if managed properly it runs with less background and in turn provides a superior product -- that's just my 2 cents.
People like shiny things, KVM/XEN seem shiner to me.
Someone has told me that "Xen" sounds cooler than "OpenVZ or KVM"
Also, fun fact, for the moment CentOS 6 dropped XEN support -- perhaps it is less shiny now?
Also, @simplenode I believe you just made a fact.
lol
Oh please somebody give me a good reason
@Jun
OpenVZ better than Xen?
That just ain't accurate.
Please, continue.
BSD OS and kernel/package developer? there's many reason here and out there but this both reason came in my first thought.
We prefer Xen/KVM over OpenVZ because we need full control over kernel and iptables.
AFAIK, OpenVZ has way much better performance than any other virtualization methods.
Why is that?
What I know is: OpenVZ has less virtualization overhead which leads to better performance.
I need full iptables access
@gbshouse @winston can't the provider enable the needed iptables modules?
@Corey - not all of them
Some people came up with iptables...
But I can't get it.
I know there are some exceptional cases that special modules are needed for some special features of iptables such as mac address filtering, but for common use, most providers do load netfilters/iptables.
@Jun I guess it all comes down to more control of the system from more isolation from the virtualization system.
Summer...
Yes. I get it. But my point is - do you really need more isolation?
Somebody who thinks a container is the same as a virtual machine doesn't know the difference.
yes. especially from summer hosting who trying to do vzctl enter/exec my CTID..
@Damian
-Well for starters you get more access and its more isolated.
-Not to mention that with openvz nothing I ever need is there. Like modules, and such.
The permissions are different, so if you want module changes you have to contact your host, which in xen you dont (Example: PPP Modules), with Xen, its all just their.
Which is an hour wasted out of your life trying to install stupid modules needed that Xen already has.
-Have you tried basic things like zipping directories with multiple files inside? or moving files? Xen is ALOT faster. Even if the specs are the exact same, Xen will finish the task's alot faster.
-OpenVZ just sucks when it comes to doing any type of gaming applications.
Packet loss is higher, and as you can imagine, when playing a FPS game, you want your servers to be low packet loss, and be able to complete tasks quickly.
Xen can complete these tasks in half the time it takes openvz to do them.
Sure if your just doing webhosting, fine, openvz is perfect for you. But Xen is better in almost every way besides price.
@Jun - for example this
@Cirium
Thanks a lot! Sounds like XEN is better options now.
Is the OpenVZ/KVM/Xen is not the same with virtual machine? Like the one we created with VMWare?
Sorry to ask, because I don't know about virtualization.
@BigScoots for my personal use I didn't mind OpenVZ until I've hit the wall again and again with trying to set up firewall rules, purge the cache memory, run custom kernels and so on inside an OpenVZ VM. Both Xen and KVM require more resources: Xen takes up RAM for itself to virtualize hardware and run, KVM needs better I/O performance. Xen can be a bitch to maintain since Red Hat has discontinued support for it. Xen PV offers the best resource management and a very granular control over CPU resources. OpenVZ is not real virtualization, but is more like a glorified version jails in FreeBSD. Therefore it has no overhead so there is no performance penalty for customers. Since the kernel is shared with the host OS the customer gets a bit more RAM with OpenVZ.
So all of them have pros and cons, but all in all it comes down to this:
With OpenVZ you have a slightly lower cost of hardware and software maintenance (think templates) and you can offer cheaper VPS servers.
With Xen PV you loose some RAM to the Xen Hypervisor + some RAM to DOM 0, so for example on a 48GB server 1.5GB is gone to those two. That has to be factored into the cost of doing business. I/O Performance is great, and the virtualization overhead is minimal with Xen PV.
KVM is what Xen HVM should have been but never was and never will be. KVM is just a kernel module, but it's so so powerful. It can do full virtualization, you can run any x86 or x86-64 inside a KVM VM, resource control is pretty good, I/O performance is horrible even with all the fancy write-back cache options for virtual machines and CPU resource control isn't granular at all, not even as much as in OpenVZ. KVM was never designed for the web hosting industry, it is an enterprise product and it was designed with over-provisioning in mind.
If I needed virtualization on a small dedicated server 4 to 8GB RAM, I would use OpenVZ. For medium to large servers I pick KVM (I like to run FreeBSD once in a while) and for customers we use Xen PV until KVM matures some more.
We tried to sell OpenVZ virtual servers to customers back in December when we started, and customer laughed at us. We got allot of the overselling arguments from different people, so we got rid of OpenVZ. Like any business, we are customer driven.
One more thing: out of this trio, KVM is the easiest to oversell, not OpenVZ, so anyone complaining about OpenVZ being easy to over-provision is [insert your favorite insult here]. Here is how you can oversell KVM:
KVM will use Swap when over-provisioned and treat it like real RAM.
Ok. We have legit reasons, I hope? OpenVZ doesn't have "internal"/"private" IPs and we need to reduce latency between our clusters as much as possible.
OpenVZ with burst also fails with any application that uses a lot of virtual memory and memory mapped files. It just crashes. VSwap fixes it to some extent but not completely since it is still very limited.
@vpsnodebox holy response! and my answer to it is ... yes.
Customers who use a properly configured OpenVZ machine see the efficiency benefits, but it is certainly a bit finiky when starting to offer it as there are some work arounds necessary. Generally I feel its a better solution in most cases, not all. In the ones its not, that is what all you guys are for
@Concerto49
Any virtualization platform can have internal IP's, it's not hard to set it up.
@BigScoots To be honest we will make the jump to KVM in the near future. Xen is wasteful with RAM and the official virtualization for Linux supported by both Red Hat and Ubuntu is KVM. In the upcoming version of SolusVM (in case you guys are using it) - KVM template support is added along with some improvements. The good thing is that you can easlily convert your existing OpenVZ nodes to KVM nodes without needing to reinstall everything. So KVM will be much easier to deplay in the coming month or so.
We have to maintain our own Xen setups, test & update our kernel, etc., and so KVM would be a welcome change.