Comments on Tales of a Code Monkey: The truth about KVM and Xen

Took me awhile to read all the comments, but I rea...

2011-12-08T02:01:34.540-08:00

Took me awhile to read all the comments, but I really love the article. It proved to be very useful to me and I am sure to all the commenters here! It's always nice when you can not only be informed, but also engaged! I'm sure you had fun writing this article.

really an informative one it was very helpful to m...

2011-12-08T02:00:41.801-08:00

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Your blogs usually possess a lot of really up to d...

2011-12-06T09:46:25.670-08:00

Your blogs usually possess a lot of really up to date info. Many thanks for sharing this first-class write-up. Very interesting ideas!

I am extremely impressed thanks for sharing all in...

2011-11-20T17:57:34.488-08:00

I am extremely impressed thanks for sharing all information. It is a great post for the people to get the proper information.

I think this has collapsed since Xen is now part o...

2011-11-01T11:23:45.930-07:00

I think this has collapsed since Xen is now part of the official Linux kernel. Never say never... LoL

unsubsribed.

2011-10-21T12:48:32.248-07:00

unsubsribed.

Too much spam... Do something, please.

2011-10-21T12:48:18.012-07:00

Too much spam...
Do something, please.

I have enjoyed this post. Its an informative topic...

2011-10-21T12:42:10.663-07:00

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Well done! I am greatful that you have shared this...

2011-09-22T02:55:26.299-07:00

Well done! I am greatful that you have shared this important list with me. Thanks! Your blog is attention-grabbing. I feel affection for it.

Hey, hope you're still in this blog, dropped b...

2011-06-26T19:02:55.825-07:00

Hey, hope you're still in this blog, dropped by and I thought that Xen got mergered ;)

You are so very-very kind. I love your blog and co...

2011-05-06T03:41:31.732-07:00

You are so very-very kind.
I love your blog and consider it an honor to be mentioned by you! This is so nice think and great stuff. I like you're ideas.

@saman Thanks for sharing your thoughts, But have...

2010-08-03T03:52:33.138-07:00

@saman

Thanks for sharing your thoughts,
But have you ever heard of paragraphs & sentence structure?

Makes it more likely that people will come away with a good taste in their mouth.

So far I have followed and understood the discussi...

2010-08-02T18:49:51.287-07:00

So far I have followed and understood the discussion, for me it seems like its about: type2 hypervisor is the evil thing and type1 is just non+ultra thing. And that's just philosophic!
XEN was developed in a time where there was no hardware support for CPU virtualization (hardware assisted virtualization). Just like in the early 90's where there was no hardware support for 3D graphics and the solution was writing software that does the job (D3D or MesaGL).
I think KVM is just better than XEN, as XEN is just like wasting time to optimize a piece of software that is going to be replaced by hardware instructions. We are still just in the era of first generation of hardware assisted virtualization CPU's. And I think that both type2 (vmware-server ...) and type1 hypervisors (XEN) are moving from CPU paravirtualization to HVM. And the prove of concept is that you can achieve nearby native OS performance with HVM when using a good implemented modren virtualization solution like KVM. It was amazing in the past to see XEN achieving native performance when there was no hardware support for virtualization (so XEN is a pure software virtualization solution). I think in the near future the terms type1 or type2 hypervisors will disappear as we are definitely moving to wards HVM. As of IO subsystems like networking or disk device subsystem, KVM was the first that successfully implemented the paravirtualization architecture for disk and network subsystem in combination with HVM and THEN XEN followed. And routing network or disk IO through a virtual machine (Dom0) and then provide it to another one is due to the lack of a multipurpose kernel like Linux and this is not really a solution, its more a work around ;). We can just see the benefits of a multipurpose kernel (Linux) when it comes to networking or disk subsystem stuff like DRBD of Linux Softraid to build HA virtualization solutions which plays much better with KVM than with XEN. Because most of that stuff is just optimized for the Linux multipurpose kernel. In the case of XEN we have to go on and re implement and optimize all that stuff like software CPU virtulisation (modified guest kernel) and DRBD and hardware drivers for a XEN kernel and lots more ...
I can just confirm Anthony
cheers

never really looked into openvz, thanks for the su...

2010-01-07T05:40:19.979-08:00

never really looked into openvz, thanks for the suggestion!

so is there a really lightweight distro around ...

2010-01-07T01:41:23.709-08:00
so is there a really lightweight distro around now that focuses purely on this kernel-based hypervisor, supporting userspace apps/GUI, & removes anything not needed?

Check out Proxmox VE. It support both KVM og OpenVZ. It's easy to install and everything is managed by a web interface.
http://pve.proxmox.com/wiki/Main_Page

It's redhat's baby, they should have a spe...

2009-11-03T23:30:25.697-08:00
It's redhat's baby, they should have a specialised distro for it.

Like all the different flavours ubuntu brings out...

They should bring out a kvm-focused one.

nice to read all the posts here. I use virtualiza...

2009-11-03T23:20:27.073-08:00
nice to read all the posts here.

I use virtualization since several years to run different systems from Linux to *BSDs as part of my business. I like Linux and use it since 1993, but the most importants for me are: performance, availability and flexibility on high load servers.

Since around one year i follow KVM and tried it several times, but until today it seems not to be an alternative for me on servers. On my desktops KVM is still used.

May be im wrong and/or this will change in the future, but really less important is that i use a "plain linux" - most of our servers are still running mixed linuxes and *BSDs (as you said, there are different OS for different application areas). The Xen hypervisor is available with linux or *BSDs - from my view it is just a tool which does his job as it should.

But i agree that the current politics of linux distributions which are installing xen or KVM hosts/guests by default is a bad idea. If a user explicitely wants to use virtualization he ill install that byself.

Unhfortunately the current discussions about KVM, XEN & Co. seems still to hot which makes nearly impossible to make a serious decision for or against KVM at the time.

Cheers,

Niels.
---
Syndicat IT&Internet

so is there a really lightweight distro around now...

2009-08-22T09:52:10.157-07:00
so is there a really lightweight distro around now that focuses purely on this kernel-based hypervisor, supporting userspace apps/GUI, & removes anything not needed?

I had a quick look at the main KVM site and it looks as though there's support to add it to some of the main distros, but I want something much more cut-down....

cheers,
jed
virt n00b

Anthony? Anyone else? Any advice greatly appreciat...

2009-08-15T09:45:53.929-07:00
Anthony? Anyone else?
Any advice greatly appreciated.

Cheers

Anthony/anyone? Any advice regarding my prior pos...

2009-08-08T22:18:51.166-07:00
Anthony/anyone?

Any advice regarding my prior post would be very much appreciated.

all the best,
jed

2009-08-08T06:57:34.232-07:00
This comment has been removed by the author.

so is there a really lightweight distro around now...

2009-08-08T06:55:36.765-07:00
so is there a really lightweight distro around now that focuses purely on this kernel-based hypervisor, supporting userspace apps/GUI, & removes anything not needed?

I had a quick look at the main KVM site and it looks as though there's support to add it to some of the main distros, but I want something much more cut-down....

cheers,
jed
virt n00b

i don't know much about either Xen or KVM, (wh...

2009-08-01T04:23:53.514-07:00
i don't know much about either Xen or KVM, (which is why i am reading this) but having played with SUN "Sparc 4v" architecture i really like their method of "Virtualising" hardware i.e a Hypervisor in the Service Processor to create LDOM's. (no need for full OS to provide VE) i know it is hardware dependent (which x86/x86_64) can be limited, but is there a similar type of virtualsation avaialble on Linux, i.e primarily to have an advantage if a panic or reboot happens in any ldom, it doesn't affect the other. is this the case with any of the Linux virtualisation techniques

Just because something ISN'T the Linux kernel does...

2009-04-16T18:38:00.000-07:00
Just because something ISN'T the Linux kernel doesn't mean distros shouldn't or won't include it.

Distros include tools like EMACS, but they're not the Linux kernel. If there are people who want to run Linux within a true hypervisor, there will be some people offering a distribution that will work for this purpose.

There's nothing wrong with having a Linux distribution choose to virtualize Linux under a purpose-built kernel, when virtualization software is chosen to be installed.

Anthony: Sometimes Type II VMs DO require OS modification. For example, VMware Server is a Type 2 VMM.

The Linux version of VMware Server requires kernel modules and OS modification to work, but that doesn't make it a hypervisor.

KVM is not a type I Virtual Machine Monitor. What sets true Hypervisors apart from hosted options like Linux KVM, is that a Hypervisor is by definition not a general-purpose OS.

Hypervisors do not run programs, they run only virtual machines.
What makes KVM not a hypervisor is the fact the kernel does normal duty as well (you can run programs directly on the 'host' OS).

You can see the kernel module in the VBox source t...

2009-03-10T12:24:00.000-07:00
You can see the kernel module in the VBox source tree which certainly proves it's a "bare metal" hypervisor. See here although the Linux glue is elsewhere in the tree.

FWIW, KVM all "modifies" the guest kernel to improve performance of guests. There are paravirtual IO drivers available for both Linux and Windows and Linux guests are capable of a number of paravirtualizations through paravirt_ops.

But I don't necessarily see how paravirtualization has anything to do with production quality.