KQEMU 1.3.0pre10 released - under the GPL

Posted Feb 7, 2007 10:38 UTC (Wed) by irios (guest, #19838)
Parent article: KQEMU 1.3.0pre10 released - under the GPL

Am I the only one that is totally confused with all the options there are for virtualization?

I can recall kvm, xen, qemu, kqemu, user mode linux, virtual box, vmware (player, server and whatnot), Microsoft's virtualization solution, Win4Lin ... Parts of some are included in others, some seem to be compatible with others, some are totally free, some partially free, some only free as in beer, some totally unfree.

Is one solution going to become the winner, or maybe a couple, or is the panorama going to get muddier and muddier? Anybody knows of a good reference comparing the abilities of the different virtualizers?

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KQEMU 1.3.0pre10 released - under the GPL

Posted Feb 7, 2007 12:26 UTC (Wed) by 01101010 (guest, #43187) [Link]

There will not be a winner, different virtualizers exist for different needs. Do you need complete emulation of an x86-system on any architecture? Only Bochs provides that, because it simulates a PC using C. But it is slow. If your CPU is supported by QEMU, which recompiles some code on the fly, it will not be that slow. Qemu can emulate different CPUs, not only x86. The common case of emulating x86 on x86 can be faster using native code execution when possible. KQemu and virtualbox do that (both extend qemu). Does your CPU support VT? Use KVM, then Qemu just has to emulate the hardware around the CPU. Dont want a full OS on top of the emulated machines? Xen provides that, also using VT and Qemu. Can still be faster if your guest os can be ported to the virtualizer, so you don't have to emulate complete hardware. Xen can do that. lguest uses a usual linux kernel as the hypervisor instead of Xen, but is slower and does not have all the interesting features Xen has (SMP, live migration). User mode linux is a port running as a userspace process, but cannot reach the speed of Xen. Sometimes you don't even want seperate kernels, just isolated userspace environments. That saves ram and is easier to manage. OpenVZ provides that.

So I think Qemu, either Qemu+KQemu or Virtualbox, Qemu+KVM, Xen, Xen+VT+Qemu, OpenVZ and something like lguest will stay alive for a long time, because each has a different approach. But that seems to be a full panorama.

KQEMU 1.3.0pre10 released - under the GPL

Posted Feb 8, 2007 13:27 UTC (Thu) by drag (guest, #31333) [Link] (2 responses)

I wrote something a while ago. Keep in mind that I am very amature at this sort of thing. http://aplawrence.com/Linux/kvm_virtualization.html

Pretty innaccurate, but I suppose you can get my meanings by my descriptions. I know more about this stuff now.

Basicly you have hypervisors, VM-as-a-application, containers, and emulation. All these things overlap to one degree or another and it's very difficult to put some things into nice catagories.

But generally speaking you have hypervisors. Examples are going to be like Xen or Vmware ESX. These things are specialized kernel-like things that are specially designed to create VMs. Then in addition you'll have a userland based on a OS to manage and provide I/O emulation. Both of these things use Linux for that to one extent to another.

These provide the highest level of sophistication, isolation, and management options and generally have the best performance of a VM capable of running different sorts of operating systems. The most 'Enterprise'ish.

Then you have VM-as-a-application stuff. Like Qemu, or Vmware's Server/Workstation/player stuff. These things are more convient, but are subject heavily to the performance limitations of the host OS combined with the performance limiations of the hosted OS along with some emulation overhead. Not the fastest, but not the slowest either. Offer good-enough performance for the majority of tasks you'd want to do in a VM.

Something like KVM actually turns the Linux kernel into a hypervisor, but in practice it seems more like the second catagory.

Then you have container-type things. Like Vserver, or OpenVZ. Think about those things as 'chroot on steroids'. They share the same kernel and work about the same as a chroot, but are designed for much higher security and isolation then what is normally possible. Since there is no software vm or emulation of anything going on these provide the highest performance and most efficient use of resources. Much better then anything else. The downside is that a kernel exploit can open up all your VM's.. and you can't run anything that is not the same as the host OS.

Then you have something like Usermode Linux. It's sort of like Vserver, but is more like a real VM. You can't run anything like Windows in it, but it does provide higher level of isolation and such.

Then you have emulation. Bochs is the best example I can think of. It's a full-on computer-expressed-in-software. Everything is in software. Software sound card, software video card, software cpu, etc etc. The whole ten yards. With this you can run x86 code on Sparc or PowerPC or anything else, it's full software. It's also very slow.

For a more expert overview check out:
http://virt.kernelnewbies.org/TechComparison

KQEMU 1.3.0pre10 released - under the GPL

Posted Feb 8, 2007 20:16 UTC (Thu) by nix (subscriber, #2304) [Link]

The same techniques are used elsewhere, of course: for instance, valgrind
is a single-process caching JITting dynamic recompiler for x86-and-PPC
assembler with instrumentation support; as such, it's fairly close to
QEMU, but with all the complexity hidden from the user.

KQEMU 1.3.0pre10 released - under the GPL

Posted Feb 9, 2007 11:46 UTC (Fri) by irios (guest, #19838) [Link]

Thanks, I've got a much clearer picture now.