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Kostas Psilopoulos 03-27-2012 06:51 PM

Xen vs KVM
 
Just proposing my opinion in this topic.

I'm in favor of XEN especially in use with debian. Most reasons have already been discused
but i'd like to add that xen is type 1 hypervisor. The very nature of Xen is completely different than
KVM. It supports the widest variety of operating systems (not that KVM does not support them,
but just comparing their performance...). One thing that might be slight better in favor of
KVM is sometimes when the guest OS uses the same kernel with the host. this happens because the host
does not generate everything from scratch (or sth like that). Anyway the difference in performance i think is
minor. Everyone should experiment with both virtualization types because both Xen and KVM are at least well supported.
The specific needs of the usecase should lead you to the choice to be made!

Best regards!


> Date: Wed, 28 Mar 2012 01:55:31 +0800
> From: ubuntu.fan.2012@gmail.com
> To: aaron.toponce@gmail.com; debian-user@lists.debian.org; singapore.mr.teo.en.ming@gmail.com
> Subject: Re: Xen vs KVM
>
> On 27/03/2012 21:32, Aaron Toponce wrote:
> > On Tue, Mar 27, 2012 at 09:51:28AM +0100, Jon Dowland wrote:
> >> On Tue, Mar 27, 2012 at 01:04:57PM +0800, Teo En Ming (Zhang Enming) wrote:
> >>> When will Debian 7.0 be released? Debian with Linux Kernel 3.x
> >>> release seems very slow when all the other Linux distros already
> >>> have the latest Linux Kernel 3.x. Why do I want Linux Kernel 3.x?
> >>> Because I want to play around with Xen virtualization (dom0
> >>> required).
> >> So you want a cutting-edge kernel to play with yesterday's virtualisation
> >> technology? The mind boggles! Debian 6.0 has KVM, libvirt, virt-manager…
> > How is Xen yesterday's virtualization technology? It's fully supported by
> > Citrix XenServer and Oracle VM. Sun used it for the basis of their xVM
> > solution, and Virtual Iron used Xen for the basis of theirs as well (both
> > of whom were purchased by Oracle).
> >
> > Some will say that Xen is more stable than KVM. After being a RHEL and
> > Debian system administrator, and deploying KVM with both the commercial
> > RHEV product, and with libvrt(8) and virt-manager(1), I think I agree. I've
> > had the hypervisor kernel do some wacky stuff with KVM that I haven't seen
> > with Xen. With that said, my heart belongs to KVM, I just wish it had a bit
> > more stability.
> >
> > Xen also has a longer history of 3rd party support, and has had a longer
> > time to mature. It was just recently accepted into the mainline Linux
> > kernel, and still shows very active development. Xen also supports full
> > virtualization and paravirtualization.
> >
> > IMO, Xen isn't "yesterday's virtualization technology". It's very current,
> > stable, flexible, supported and very much "today's virtualization
> > technology".
> >
> > --
> > . o . o . o . . o o . . . o .
> > . . o . o o o . o . o o . . o
> > o o o . o . . o o o o . o o o
>
> Dear Aaron,
>
> I agree with you.
>
> Anyway, I have never used Linux KVM before. I have always supported Xen,
> since 3 years ago.
>
> --
> Yours sincerely,
>
> Mr. Teo En Ming (Zhang Enming)
> Singapore
>
>
> --
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>

"Teo En Ming (Zhang Enming)" 03-28-2012 12:32 AM

Xen vs KVM
 
I am also in favor of Xen.

--
Yours sincerely,

Mr. Teo En Ming (Zhang Enming)
Singapore


On 28/03/2012 02:51, Kostas Psilopoulos wrote:



Just proposing my opinion in this topic.



I'm in favor of XEN especially in use with debian. Most reasons
have already been discused

but i'd like to add that xen is type 1 hypervisor. The very
nature of Xen is completely different than

KVM. It supports the widest variety of operating systems (not
that KVM does not support them,

but just comparing their performance...). One thing that might
be slight better in favor of

KVM is sometimes when the guest OS uses the same kernel with the
host. this happens because the host

does not generate everything from scratch (or sth like that).
Anyway the difference in performance i think is

minor. Everyone should experiment with both virtualization types
because both Xen and KVM are at least well supported.

The specific needs of the usecase should lead you to the choice
to be made!



Best regards!





> Date: Wed, 28 Mar 2012 01:55:31 +0800

> From: ubuntu.fan.2012@gmail.com

> To: aaron.toponce@gmail.com;
debian-user@lists.debian.org;
singapore.mr.teo.en.ming@gmail.com

> Subject: Re: Xen vs KVM

>

> On 27/03/2012 21:32, Aaron Toponce wrote:

> > On Tue, Mar 27, 2012 at 09:51:28AM +0100, Jon
Dowland wrote:

> >> On Tue, Mar 27, 2012 at 01:04:57PM +0800, Teo En
Ming (Zhang Enming) wrote:

> >>> When will Debian 7.0 be released? Debian
with Linux Kernel 3.x

> >>> release seems very slow when all the other
Linux distros already

> >>> have the latest Linux Kernel 3.x. Why do I
want Linux Kernel 3.x?

> >>> Because I want to play around with Xen
virtualization (dom0

> >>> required).

> >> So you want a cutting-edge kernel to play with
yesterday's virtualisation

> >> technology? The mind boggles! Debian 6.0 has
KVM, libvirt, virt-manager…

> > How is Xen yesterday's virtualization technology?
It's fully supported by

> > Citrix XenServer and Oracle VM. Sun used it for the
basis of their xVM

> > solution, and Virtual Iron used Xen for the basis of
theirs as well (both

> > of whom were purchased by Oracle).

> >

> > Some will say that Xen is more stable than KVM.
After being a RHEL and

> > Debian system administrator, and deploying KVM with
both the commercial

> > RHEV product, and with libvrt(8) and
virt-manager(1), I think I agree. I've

> > had the hypervisor kernel do some wacky stuff with
KVM that I haven't seen

> > with Xen. With that said, my heart belongs to KVM, I
just wish it had a bit

> > more stability.

> >

> > Xen also has a longer history of 3rd party support,
and has had a longer

> > time to mature. It was just recently accepted into
the mainline Linux

> > kernel, and still shows very active development. Xen
also supports full

> > virtualization and paravirtualization.

> >

> > IMO, Xen isn't "yesterday's virtualization
technology". It's very current,

> > stable, flexible, supported and very much "today's
virtualization

> > technology".

> >

> > --

> > . o . o . o . . o o . . . o .

> > . . o . o o o . o . o o . . o

> > o o o . o . . o o o o . o o o

>

> Dear Aaron,

>

> I agree with you.

>

> Anyway, I have never used Linux KVM before. I have always
supported Xen,

> since 3 years ago.

>

> --

> Yours sincerely,

>

> Mr. Teo En Ming (Zhang Enming)

> Singapore

>

>

> --

> To UNSUBSCRIBE, email to
debian-user-REQUEST@lists.debian.org

> with a subject of "unsubscribe". Trouble? Contact
listmaster@lists.debian.org

> Archive: http://lists.debian.org/4F71FF13.505@gmail.com

>

Jon Dowland 03-28-2012 08:35 AM

Xen vs KVM
 
On 27/03/12 14:32, Aaron Toponce wrote:

IMO, Xen isn't "yesterday's virtualization technology". It's very
current, stable, flexible, supported and very much "today's
virtualization technology".


For me, it became yesterday's technology when it became apparent that
the hypervisor model (putting an entirely new kernel between Linux and
the hardware) created all sorts of performance problems, and neglected
the decades of work that had gone into the Linux network stack, amongst
other parts. Increasingly ugly hacks were (are) needed to pass through
to the privileged domain, all of which is totally unnecessary with the
KVM model, where the (much more) tried and tested Linux kernel goes on
the bottom of the pile.

Paravirtualisation had a brief moment of popularity before VT hardware
became so prevelant to make it unnecessary any more. PV was basically
the USP of Xen back in the day.

I sympethize that you have faced problems with KVM that you hadn't seen
with Xen. I've had the opposite experience myself.

In general I think the management tools are much more important than the
base VM tech.


--
Jon Dowland


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Jon Dowland 03-28-2012 08:36 AM

Xen vs KVM
 
On 28/03/12 01:32, Teo En Ming (Zhang Enming) wrote:

I am also in favor of Xen.


You have just said, not two messages ago, that you've never even tried
KVM. I always prefer to base my opinions on evidence, personally.



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Aaron Toponce 03-28-2012 01:43 PM

Xen vs KVM
 
On Wed, Mar 28, 2012 at 09:35:25AM +0100, Jon Dowland wrote:
> For me, it became yesterday's technology when it became apparent that
> the hypervisor model (putting an entirely new kernel between Linux and
> the hardware) created all sorts of performance problems, and neglected
> the decades of work that had gone into the Linux network stack, amongst
> other parts. Increasingly ugly hacks were (are) needed to pass through
> to the privileged domain, all of which is totally unnecessary with the
> KVM model, where the (much more) tried and tested Linux kernel goes on
> the bottom of the pile.

Can you expound on these "ugly hacks"? The Xen kernel is a full type-I
hypervisor, with unfettered access to the hardware. The dom0 presents the
virtualized hardware to the domU guests. Using Xen HVM, the presentation
uses Qemu, which is exactly the same for KVM.

--
. o . o . o . . o o . . . o .
. . o . o o o . o . o o . . o
o o o . o . . o o o o . o o o

Hilco Wijbenga 03-28-2012 04:44 PM

Xen vs KVM
 
On 28 March 2012 06:43, Aaron Toponce <aaron.toponce@gmail.com> wrote:
> On Wed, Mar 28, 2012 at 09:35:25AM +0100, Jon Dowland wrote:
>> For me, it became yesterday's technology when it became apparent that
>> the hypervisor model (putting an entirely new kernel between Linux and
>> the hardware) created all sorts of performance problems, and neglected
>> the decades of work that had gone into the Linux network stack, amongst
>> other parts. Increasingly ugly hacks were (are) needed to pass through
>> to the privileged domain, all of which is totally unnecessary with the
>> KVM model, where the (much more) tried and tested Linux kernel goes on
>> the bottom of the pile.
>
> Can you expound on these "ugly hacks"? The Xen kernel is a full type-I
> hypervisor, with unfettered access to the hardware. The dom0 presents the
> virtualized hardware to the domU guests. Using Xen HVM, the presentation
> uses Qemu, which is exactly the same for KVM.

You might both be interested in the PDF linked to at the bottom of
[1]. It explains why Qubes OS went with Xen and not KVM. I thought it
was quite interesting (I used to be firmly in the KVM camp, now I'm
not sure any more. :-) ) Mind you, their focus is mainly security.

[1] http://www.qubes-os.org/Architecture.html


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francis picabia 03-29-2012 04:32 PM

Xen vs KVM
 
On Wed, Mar 28, 2012 at 1:44 PM, Hilco Wijbenga
<hilco.wijbenga@gmail.com> wrote:
> On 28 March 2012 06:43, Aaron Toponce <aaron.toponce@gmail.com> wrote:
>> On Wed, Mar 28, 2012 at 09:35:25AM +0100, Jon Dowland wrote:
>>> For me, it became yesterday's technology when it became apparent that
>>> the hypervisor model (putting an entirely new kernel between Linux and
>>> the hardware) created all sorts of performance problems, and neglected
>>> the decades of work that had gone into the Linux network stack, amongst
>>> other parts. Increasingly ugly hacks were (are) needed to pass through
>>> to the privileged domain, all of which is totally unnecessary with the
>>> KVM model, where the (much more) tried and tested Linux kernel goes on
>>> the bottom of the pile.
>>
>> Can you expound on these "ugly hacks"? The Xen kernel is a full type-I
>> hypervisor, with unfettered access to the hardware. The dom0 presents the
>> virtualized hardware to the domU guests. Using Xen HVM, the presentation
>> uses Qemu, which is exactly the same for KVM.
>
> You might both be interested in the PDF linked to at the bottom of
> [1]. It explains why Qubes OS went with Xen and not KVM. I thought it
> was quite interesting (I used to be firmly in the KVM camp, now I'm
> not sure any more. :-) ) Mind you, their focus is mainly security.
>
> [1] http://www.qubes-os.org/Architecture.html
>

Xen requires a patched kernel. It is unstable. It crashed on
me randomly before I got as far as configuring any VM stuff.
The system which experienced this returned to a standard
Debian kernel and never had a problem again.

KVM is native part of kernel. It is stable. I've been running on several
systems for over a year and no crash.

Both share the same qemu devices and drivers land.

You can read what IBM has to say about key benefits and security
features of kvm...

ftp://ftp.software.ibm.com/linux/pdfs/LXW03004-USEN-00.pdf

A big clue is Redhat is dropping xen virtualization going forward.

Kvm will get more development support than xen.

I see no reason to even consider xen.


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"Teo En Ming (Zhang Enming)" 03-30-2012 05:27 AM

Xen vs KVM
 
On 28/03/2012 16:35, Jon Dowland wrote:

On 27/03/12 14:32, Aaron Toponce wrote:

IMO, Xen isn't "yesterday's virtualization technology". It's very
current, stable, flexible, supported and very much "today's
virtualization technology".


For me, it became yesterday's technology when it became apparent that
the hypervisor model (putting an entirely new kernel between Linux and
the hardware) created all sorts of performance problems, and neglected
the decades of work that had gone into the Linux network stack, amongst
other parts. Increasingly ugly hacks were (are) needed to pass through
to the privileged domain, all of which is totally unnecessary with the
KVM model, where the (much more) tried and tested Linux kernel goes on
the bottom of the pile.

Paravirtualisation had a brief moment of popularity before VT hardware
became so prevelant to make it unnecessary any more. PV was basically
the USP of Xen back in the day.

I sympethize that you have faced problems with KVM that you hadn't seen
with Xen. I've had the opposite experience myself.

In general I think the management tools are much more important than the
base VM tech.



Dear Jon Dowland,

I beg to differ. Xen virtualization offers superior performance. Oracle
VirtualBox and Virtual Iron and also Microsoft's Hyper-V is based on Xen
code I think.


Thank you very much.

--
Yours sincerely,

Mr. Teo En Ming (Zhang Enming)
Singapore


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"Teo En Ming (Zhang Enming)" 03-30-2012 05:29 AM

Xen vs KVM
 
On 28/03/2012 16:36, Jon Dowland wrote:

On 28/03/12 01:32, Teo En Ming (Zhang Enming) wrote:

I am also in favor of Xen.


You have just said, not two messages ago, that you've never even tried
KVM. I always prefer to base my opinions on evidence, personally.





Yes, I have never tried Linux KVM. But I have tried VirtualBox and VMware.

--
Yours sincerely,

Mr. Teo En Ming (Zhang Enming)
Singapore


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wlan 03-30-2012 05:34 AM

Xen vs KVM
 
On my job we using KVM+Proxmox, This is pretty.

2012/3/30 Teo En Ming (Zhang Enming) <ubuntu.fan.2012@gmail.com>

On 28/03/2012 16:36, Jon Dowland wrote:


On 28/03/12 01:32, Teo En Ming (Zhang Enming) wrote:


I am also in favor of Xen.




You have just said, not two messages ago, that you've never even tried KVM. *I always prefer to base my opinions on evidence, personally.








Yes, I have never tried Linux KVM. But I have tried VirtualBox and VMware.



--

Yours sincerely,



Mr. Teo En Ming (Zhang Enming)

Singapore





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