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KVM steals virtualization spotlight (ZDNet)KVM steals virtualization spotlight (ZDNet)Posted Feb 26, 2007 23:22 UTC (Mon) by drag (subscriber, #31333)Parent article: KVM steals virtualization spotlight (ZDNet)
Bah.
KVM kicks-ass. Seriously.
You know what is the difference between Xen and KVM?
KVM is usefull for normal people. It's sane, it's aviable by default, and it doesn't destabilize the system.
If you want to setup a seperate server for your Linux box, then KVM is the easy and sane approach. If you want to setup a VM for legacy applications (say some propriatory app that only supports Redhat 9, or your migrating from Windows desktop) then KVM is MUCH more suitable.
And what is this business about 'maturity' between KVM and Xen? Sure Xen has more features, but KVM has Qemu and the Linux kernel backing it up.
Fair trade I figure, more then fair.
Xen is intrusive and difficult to use and manage in comparision. It took many years for Xen to reach the point were KVM took months. If XenSource people figure they can sell propriatory software (aka XenEnterprise) to deal with that aspect of it and that people will choose that over KVM then they are sadly mistaken.
Seriously:
And what is this hypervisor versus application layer stuff. Is that FUD or something?
I thought that KVM effectively turned the Linux kernel into a hypervisor, rather then a sort of 'kernel-mode' accelerator for making emulation faster. I don't understand this aspect all that much.
So on one side you have Qemu + KVM, Qemu + Kqemu (recently GPL'd) versus Xen on the other.
Why fight?
It's obvious that they realy aren't competing and probably shouldn't.
Xen is, and should, aim for the big enterprise situations were you have dozens and dozens of machines in blade servers and such. High density hardware with lots of ram and centralized SAN storage to be able to leverage the load balancing aspects and system management advantages of having 'floating system images'. Virtual machines migrating around from machine to machine as needed floating around on a thin layer of hypervisor.
KVM is more suitable to desktop oriented applications.
A howto on getting your Windows applications to appear to integrate into your Linux desktop. The leverages Qemu heavily along with Rdesktop.
Now with KVM/Qemu a administrator could setup a bunch of people with Linux desktops. If they have some sort of legacy application that requires windows (for instance Fedex shipping manager application) then the admin could ftp over a windows XP pro image and have it setup transparently for that end user in probably 15-20 minutes.
Something simple and quick and effective. How much of a PITA would that be for Xen?
Or say you want to setup a secure FTP server or DNS server and don't trust Vserver enough for the paticularly hostile environment your going to expose the VM to. (a local kernel exploit in OpenVZ or Vserver-based VM would allow the attacker access to the entire machine). That would be much easier to deal with with KVM.
Or some server application you have setup on Debian Sarge, but the hardware is failing. You buy new hardware but decide to go with Ubuntu or Etch isntead, but you don't want to spend any time porting applications over to the new php version or something like that. KVM to the rescue, just pop in the old harddrives and fire them up. No sweat. Or use DD to make a file image. No sweat either.
I could go on and on were the ease of use and nature of KVM makes it more suitable then Xen.
So they are complementary, not competing in my eyes.
In fact I think that KVM is such a powerfull asset for the Linux desktop especially that all desktop-oriented distributions should ship with the full suite of KVM/KQEMU/QEMU and related applications, especially GUI applications and simple scripts to deal with common VM-related network configurations...
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KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 2:34 UTC (Tue) by fjf33 (subscriber, #5768) [Link] Now maybe talking out of my ass but I think Xen's advantage was that it was less expensive resources wise. So for desktop use, and light server use KVM is better, but for a heavy loaded virtualized server Xen is better.
I am sure the performance gap will close up fast. Particularly since KVm avoids the out of kernel maintenance overhead. Things that are mainlined in the kernel tend to get fresher ideas thrown at it.
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 3:18 UTC (Tue) by nlucas (subscriber, #33793) [Link] I also think KVM is the way to go, and I already knew it even before it appeared (was just a question of time until someone did it). But you are forgeting some things, like the fact that if KVM was so "easy" to do was because of the kernel changes introduced by Xen and other [para-]virtualization/containers hackers. You could even say KVM just took advantage of the hard work of others.
Also, we are still waiting for the implementation of generic KVM para-virtualization. I have a very recent CPU (a Pentium D 945) but it doesn't support the hardware hypervisor extensions, so qemu+kqemu or even Xen is better than KVM for me (at least it works).
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 4:14 UTC (Tue) by drag (subscriber, #31333) [Link] You CPU should support VT. I have a Pentium-D 930 and it supports VT and I've run KVM on it.
The trouble could be the motherboard. You need both to support VT in order to use the extensions. I have a Asus unit with a intel 945G chipset.
Look for BIOS settings. I beleive that sometimes BIOS upgrades can possibly enable the VT extensions so look fro a bios upgrade if you can't find any settings. By default the VT stuff was disabled in my BIOS.
The Pentium-D 8xx proccessors don't support VT, but the Pentium-D 9xx should.
The nice thing about Qemu + Kqemu and Qemu modified to support KVM is that images should work in both setups. Also they can run non-ported OSes (ie: Windows or SCO or whatever) were as Xen cannot without the VT extensions themselves.
But I do understand. I run Xen on my fileserver at home since it's just a AMD Althon XP. I have 2 nic cards, one is a Intel GB/s card and that goes to my lan, and then the onboard 100Mb/s goes to the 'DMZ' port on my Debian/Shorewall-based router. That way if the internet-facing server running in the VM gets compromised my home lan is still completely isolated. Good stuff. :-)
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 14:28 UTC (Tue) by nlucas (subscriber, #33793) [Link] 940 has VT, 945 doesn't (needs to end with a 0).
When I bought the CPU there were no 9x0 available in stock (and no prevision of when there would be), so I ended up buying the one without VT.
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 20:28 UTC (Tue) by drag (subscriber, #31333) [Link] Oh realy.
That sucks, I thought all 9xx proccessors supported it.
KVM steals virtualization spotlight (ZDNet) Posted Feb 28, 2007 17:45 UTC (Wed) by aliguori (subscriber, #30636) [Link] like the fact that if KVM was so "easy" to do was because of the kernel changes introduced by Xen and other [para-]virtualization/containers hackers. That's not true. KVM in 2.6.20 doesn't use paravirt_ops. Besides, paravirt_ops was largely based on VMI.
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 16:11 UTC (Tue) by mmarq (guest, #2332) [Link] "" Xen is intrusive and difficult to use and manage in comparision. It took many years for Xen to reach the point were KVM took months. ""
agreed...
"" And what is this hypervisor versus application layer stuff. Is that FUD or something?... ...So on one side you have Qemu + KVM, Qemu + Kqemu (recently GPL'd) versus Xen on the other. ""
.- KVM is a *Monitor* inside the Linux kernel.
.- Xen is an exokernel derived from the Nemesis OS, running in hypervisor, with the *Monitor Management* stuff inside. I belive Xen is *very natural* at the Monitor thing, because the original idea of an exokernel is already to protect, partition and multiplex the hardware resources, and live the schedular, mem and interrupts management to applications and or libOSes.
Can the two co-exist togheter ?
I belive they can, if the *Monitor Management stuff* stays with KVM, but Linux uses Xen as a domain generator and manager, that is, a VM stays as a Linux process but inside a "Xen" domain !... can Linux use a "Xen hypervisor" to put a VM process inside a protecting domain with migration abilitys ?
Now we would have something like Qemu as a VM ( dont know, but possibly maintaining the ability to emulate Power or Sparc also) as a Linux process but running inside a protection domain with migration abilitys!...
That would be something !...
BETTER, because now if Xen is striped out of the strict Monitor Management function, it can include something like Ipipe, that is, "Xen" switches a VMM for an Ipipe, and everybody will win twice.
Because now we get Linux with a blazing fast VMM stuff with domain migration, and with deterministic hard real-time abilitys!
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 19:04 UTC (Tue) by mikov (subscriber, #33179) [Link] Any word on performance of Xen vs KVM ?
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 20:34 UTC (Tue) by drag (subscriber, #31333) [Link] Xen's paravirtualization is MUCH faster then anything else. Very little overhead.
For Xen total virtualization utilizing VT/SVM vs KVM I don't know, but I expect Xen to be faster.
For Vmware vs Xen/KVM virtualization then Vmware is fastest due to it's highly optimized software emulation. The current generation of hardware assisted virtualization isn't that hot.
I think that KVM still needs work to do for some memory management items and such to get it up to performance, but the Linux kernel guys seem to have done a lot of very nice work with it.
It would be interesting to see some benchmarks on it.
KVM steals virtualization spotlight (ZDNet) Posted Feb 28, 2007 22:09 UTC (Wed) by mikov (subscriber, #33179) [Link] Xen's paravirtualization is MUCH faster then anything else. Very little overhead. Yes. So, practically speaking, it only makes sense to use KVM if you wanted to run Windows. For Linux guests paravirtualization will always be much faster. Then I don't see what all the excitement really is about.
KVM steals virtualization spotlight (ZDNet) Posted Mar 1, 2007 3:06 UTC (Thu) by drag (subscriber, #31333) [Link] Ever used Xen?Then you use KVM?
Ever try to use either on your personal desktop?
Then it becomes obvious. :-)
Plus there are a lot of unported OSes out there to play around with or you may need for one reason or another.
Some examples:
Here is a example in Debian (for Kqemu)
Make a directory to house the images.
select 'use cdrom', leave it at /dev/cdrom or point it at your iso image.
Make sure that 'boot from cdrom' is selected.
Boot and install the operating system.
After install then shutdown. Configure networking, sound, and video card as you please. Boot it up, confirm that it works and then save the configuration.
Very easy.
Btw I found a nice comparison between Kqemu and KVM aviable at:
They are both between 80 and 85% efficient at the benchmarks.
KVM steals virtualization spotlight (ZDNet) Posted Mar 1, 2007 3:21 UTC (Thu) by drag (subscriber, #31333) [Link] Oh and btw. The real cool thing about that link is that Kqemu and KVM are pretty much neck and neck when it comes to performance.
I bet with the kernel hackers tweaking everything KVM is faster now by a bit, but that doesn't mean that Kqemu isn't great if you don't have the required cpu extensions.. :-)
KVM steals virtualization spotlight (ZDNet) Posted Mar 1, 2007 12:20 UTC (Thu) by k8to (subscriber, #15413) [Link] > > Xen's paravirtualization is MUCH faster then anything else. Very> > little overhead. > > Yes. So, practically speaking, it only makes sense to use KVM if > you wanted to run Windows. For Linux guests paravirtualization will > always be much faster.
Sure, if all you care about is performance.
If being able to conveniently and easily set this stuff up matters to you, KVM begins to look a bit better. Nice management also recommends KVM. Ability to run the latest Linux kernels pushes you towards KVM as well. I would call these practical issues, myself.
Personally I am running FreeBSD and Solaris in minimized windows at the moment (some research of the cousins going on here), and the effort of setting them up and tearing them down is completely trivial. As a (mostly) unpriveledged user I can install these things and launch them with shell aliases. Very, very happy with kvm here.
The video performance with 12 was kind of assy, but it seems decent under 14 now. (I'm relying on Debian packages for my installation, so I'm not on 15 yet. Yes, it was (almost) as easy as apt-get install kvm, try this with xen!)
KVM steals virtualization spotlight (ZDNet) Posted Feb 27, 2007 21:08 UTC (Tue) by muwlgr (guest, #35359) [Link] "Seriously:Make open source software, but leave it difficult to manage. Then create propriatory software distribution to make it easier. That approach is not going to win freinds and followers."
HeHe, that's about CUPS as well :>
KVM steals virtualization spotlight (ZDNet) Posted Mar 2, 2007 20:10 UTC (Fri) by jschrod (subscriber, #1646) [Link] Yes, and sendmail.
KVM steals virtualization spotlight (ZDNet) Posted Feb 28, 2007 15:54 UTC (Wed) by k8to (subscriber, #15413) [Link] KVM is certainly what I'm using. Just installing vmware is too much hassle by comparison, even if it is no-cost for my personal use at this point.
I expect KVM to be what hackers everywhere use for the most part, and I expect large installations to continue with VMWare or play with Xen.
But then what will happen over time if all the developers are using KVM? I think we may see things begin to shift.
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