The article (yup, I've speed read TFA) defines Xen as a para-virtualization systems... Completely ignoring that since now years Xen also allows to do hardware-virtualization. Another posted also noted already that Xen's power lies in its ability to run different OSes.
Btw I happen to run my Samba / NFS / CVS / SVN server on a Xen para-virtualized domU. For hardware-virtualization I tried Xen too and the open, free, version lacks good I/O drivers for Windows (slow network and slow disk). We very well know that Xen supports hardware-virtualization as well. As you pointed out, the performance is abysmal because Xen still uses IO emulation while using hardware virtualization.
People want to Google on exactly "Which virtualization is right for you" and read infos from a knowledgable sysadmin (managing thousands of servers and virtual servers on a lot of various platforms and, no, it's not me) instead of an article performing micro-benchmarking of hypercalls to compare apples to oranges. These are NOT micro-benchmarks. Infact, I would call them macro benchmarks. A few server consolidation scenarios are setup and the performance of Xen and OpenVZ is compared. Then, we dug deeper to find out the reasons for the problems using Oprofile. It's not comparing orranges to apples, because both technologies are touted for server consolidation.
There's no single virtualization technology that works for every one, as many have explained in earlier comments.
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? We would gladly run the same kind of experiments on VMware, but VMware does not allow publishing results, unless they have a look at them first. They probably don't want unfavourable results to be published. As an academic, I really hate such restrictions and want to do an un-biased study.
> Xen's benchmarks vs. native, VM and UML are pretty decent. Not sure what cleverly crafted scenarios they're using here.
Xen for that matter any virtualization will run CPU intensive applications very well and close to native. If it doesn't, there is some thing really wrong. The problem happens in I/O intensive applications. It's not our (I am the primary author of the report) goal to find clever scenarios to find where Xen is worse. These scenarios are real and use complex multi-tier setups. These scenarios are very commonly used in server consolidation and we wanted to evaluate how Xen and OpenVZ compare. More importantly, from a research perspective, what exactly causes these trade-offs ?
P.S. These are my personal opinions and don't reflect that of HP.
HP actually works more closely with Xen than OpenVZ. For that matter, HP guys have contributed quite a bit of code to Xen (XenoProf, Perfmon come to mind). This study is done by people from U.Michigan and people at HP labs, a research division of HP.
> 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.
KVM ? Though it is in early stages of development, in theory, it may be able to run faster than Xen. It's goals, however are different from that of Xen's
> But which ones of these things can run Windows clients, at least XP? > VMWare can, User Mode Linux can't, but what about OpenVZ, Xen, and some of the others?
Xen can run Windows without para virtualization using new processor VT extensions. OpenVZ's commercial implementation Virtuozzo can run Windows on Linux.
> do any of these make USB devices visible to the client OS? > Or do they all just have to network-mount resources that are actually mounted in the host OS?
Both Xen, VMware and OpenVZ all allow access to USB devices. There are multiple ways of accessing host resources from the guest with out mounting them over network.
Slashdot Mirror
Btw I happen to run my Samba / NFS / CVS / SVN server on a Xen para-virtualized domU. For hardware-virtualization I tried Xen too and the open, free, version lacks good I/O drivers for Windows (slow network and slow disk). We very well know that Xen supports hardware-virtualization as well. As you pointed out, the performance is abysmal because Xen still uses IO emulation while using hardware virtualization. People want to Google on exactly "Which virtualization is right for you" and read infos from a knowledgable sysadmin (managing thousands of servers and virtual servers on a lot of various platforms and, no, it's not me) instead of an article performing micro-benchmarking of hypercalls to compare apples to oranges. These are NOT micro-benchmarks. Infact, I would call them macro benchmarks. A few server consolidation scenarios are setup and the performance of Xen and OpenVZ is compared. Then, we dug deeper to find out the reasons for the problems using Oprofile. It's not comparing orranges to apples, because both technologies are touted for server consolidation.
There's no single virtualization technology that works for every one, as many have explained in earlier comments.
Pradeep
Pradeep (Primary author of the mentioned report)
> Xen's benchmarks vs. native, VM and UML are pretty decent. Not sure what cleverly crafted scenarios they're using here.
Xen for that matter any virtualization will run CPU intensive applications very well and close to native. If it doesn't, there is some thing really wrong. The problem happens in I/O intensive applications. It's not our (I am the primary author of the report) goal to find clever scenarios to find where Xen is worse. These scenarios are real and use complex multi-tier setups. These scenarios are very commonly used in server consolidation and we wanted to evaluate how Xen and OpenVZ compare. More importantly, from a research perspective, what exactly causes these trade-offs ?
P.S. These are my personal opinions and don't reflect that of HP.
HP actually works more closely with Xen than OpenVZ. For that matter, HP guys have contributed quite a bit of code to Xen (XenoProf, Perfmon come to mind). This study is done by people from U.Michigan and people at HP labs, a research division of HP.
Pradeep
> 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.
KVM ? Though it is in early stages of development, in theory, it may be able to run faster than Xen. It's goals, however are different from that of Xen's
> But which ones of these things can run Windows clients, at least XP?
> VMWare can, User Mode Linux can't, but what about OpenVZ, Xen, and some of the others?
Xen can run Windows without para virtualization using new processor VT extensions. OpenVZ's commercial implementation Virtuozzo can run Windows on Linux.
> do any of these make USB devices visible to the client OS?
> Or do they all just have to network-mount resources that are actually mounted in the host OS?
Both Xen, VMware and OpenVZ all allow access to USB devices. There are multiple ways of accessing host resources from the guest with out mounting them over network.