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Performance Evaluation of Xen Vs. OpenVZ
An anonymous reader writes "Compared to an operating-system-level virtualization technology like OpenVZ, Xen — a hypervisor-level virtualization technology that allows multiple operating systems to be run with and without para-virtualization — trades off performance for much better isolation and security. OpenVZ's performance advantage due to running virtual containers in a single operating system kernel can be significant. A performance evaluation study (PDF) done by researchers at the University of Michigan and HP labs provides insight into how big a performance penalty Zen pays and what causes the overheads (primarily L2 cache misses)." From the report: "We compare both technologies with a base system in terms of application performance, resource consumption, scalability, low-level system metrics like cache misses and virtualization-specific metrics like Domain-0 consumption in Xen. Our experiments indicate that the average response time can increase by over 400% in Xen and only a modest 100% in OpenVZ as the number of application instances grows from one to four... A similar trend is observed in CPU consumptions of virtual containers."
[Xen]... "trades off performance for much better isolation and security."
No kidding, that's why I use it! Xen's performance ain't so bad. Show me a better performing virtualization solution that matches or bests Xen's isolation security - then we'll talk.
Kernel VM is based off QEMU -- but doesn't Xen have a similar hypervised Linux kernel. (I personally thought that may be why KVM was created -- to be a better Xen.) As I'll eventually upgrade to a Linux distro with KVM, I wonder if there are similarities in them -- or preferably if KVM could be fully tested and compared with these results.
From reading the article on hypervisor it still seems ambiguous. It implies that a hypervisor is not exactly a VM but the actual detailed description makes it out to be a VM. Others seem to imply it means the VM is running as an OS basically.
From everything I can see though the word is useless and it amounts to the equivalent of computer scientists being fussy. VM or VM OS are better choices.
Nothing like a virtualization comparison that ignores the 800 guerilla that is VMWare. How do the learning curves, performance and security of these products compare with VMWare? Why should someone who is satisfied with VMWare consider other alternatives?
the clock on the wall says 4 til 7
Personally i'm Xen biased due to cost.
I agree. Just a little addition: besides, VMware licenses are even more important when you want to scale. Say you want to use two quad boxes for load balancing, running VMware in each: that's about 8 x 5000 = $40000 in licenses (or $35000 if the first CPU is for free; I'm using your prices, but I knew about a similar project where VMware was decided against due to licensing costs too). You can buy more hardware with that money and train all your staff to understand and use Xen.
My weblog in spanish
I've gotta say I can't see myself ever NOT installing a server in either an OpenVZ VE or a Xen domU ever again
Remind me to never EVER hire you to do any work for me. Ever heard of "the right tool for the job"? I am a huge fan of virtualisation, and have been using it for years, VMWare mostly, but lately more and more with Xen. Given that Xen simply does not yet play nice with most of the lower cost hardware, and has several significant shortcomings in real-life enterprise production environments (running against a multihomed SAN is a not-so-distant nightmare), Xen still has some work left to do. Anyhow, I'm a huge fan of virtualisation, but there are plenty of workloads that simply do not work well virtualised, irrespective of the VM flavour du-jour you are using.
Saying you will only ever use virtualised workloads is stupid, and unprofessional. -and no, the fact that you got [oracle,mysql,postgresql] to run in a VM does not mean its going to be anywhere near decent performance.
People who think they know everything are a great annoyance to those of us who do.
There's one item you didnt list, though it might be folded under capabilities or ease of use...
Manageability is a key item for these types of setups. As people being to depend more and more on virtualization technologies (whatever those might be) and roll out virtualized production environments, you have to figure out how to monitor and manage them. This is one area where VMWare currently has the upper hand, as Xen's management API has not yet been stabilized.
The reason this is important is because with all the hype surrounding virtualization, people seem to be focused on 'getting virtualized' (server consolidation being the primary driver) rather than the consequences (application capacity issues, constant live migrations to keep things healthy, etc.).
Manageability is a key stepping stone into the enterprise. Xen's made great strides recently (both in the open source form and in the commercial form), but there's a ton of work left to do on that end to catch up to VMWare.
-javier
http://www.hyperic.com/
You missed the biggest point for a corporation; Support. No corporation looking at virtualization (and let's get real; almost all of them are) is going to use Xen OR OpenVZ at this point because there's no single point of contact for support, and no support contracts.
Quite simply, a corporation is going to buy VMWare Virtual Infrastructure. So the performance isn't as good? So what? Throw hardware at it. It works.
We have a significant investment in VMWare VI3 where I work, and it's great. We run it on high-end highly scalable enterprise hardware (IBM) and it almost never dies. We lose guests occasionally because of Windows problems, but so far we have never lost a host machine, and they never go down except when we need to maintain or upgrade them.
Last week we had a CPU die in one of our highly redundant, highly scalable boxes. Apart from the alert thrown up in MOM we practically didn't even notice the glitch. VI3 kept plugging along until we could roll the guests off to another host on the SAN and we took the box out after lunch, replaced the CPU and it was back in production within an hour. The business units who use the guests never even noticed the outage.
Note though that to a corporation, the license cost is trivial for the security that if we had a host failure (software, not hardware) then there's one number to call; EMC/VMWare. Trawling the Usenet and Google Searches don't cut it from a Corporate perspective. And let's face it, Corporations are the primary target market for virtualization, not the consumer (at least today).
As an aside, consumer level virtualization will happen soon, but it will be transparent to the user. It's probably going to be more akin to OpenVZ's "uber sandboxes" than VMWare but it will definitely happen in my opinion.