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Old 09-07-2011, 01:51 PM
Digimer
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On 09/07/2011 09:34 AM, Rudi Ahlers wrote:
> Red Hat (and thus CentOS) has native XEN support but dropped XEN in
> favor of KVM (which is not as mature yet) in RH 6.

This deserves clarification...

Red Hat is a business, and made a simple business decision. Maintaining
Xen support would have meant maintaining a very large set of patches.
They made the decision that the effort (and money) needed to maintain
Xen outside of the mainline kernel was not worth it.

KVM was not chosen over Xen so much as KVM was a much less expensive
hypervisor to support. As for it being mature or not; Well, put on your
kevlar pants because that is a matter of opinion.

As a follow-up, Xen dom0 support began getting into the mainline kernel
at 2.6.33 (EL6 is based on 2.6.32). It is very likely that we will see
Xen dom0 support returned in the next major release.

--
Digimer
E-Mail: digimer@alteeve.com
Freenode handle: digimer
Papers and Projects: http://alteeve.com
Node Assassin: http://nodeassassin.org
"At what point did we forget that the Space Shuttle was, essentially,
a program that strapped human beings to an explosion and tried to stab
through the sky with fire and math?"
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Old 09-07-2011, 01:57 PM
Always Learning
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, 2011-09-07 at 09:51 -0400, Digimer wrote:

> Red Hat is a business, and made a simple business decision. Maintaining
> Xen support would have meant maintaining a very large set of patches.
> They made the decision that the effort (and money) needed to maintain
> Xen outside of the mainline kernel was not worth it.

Perhaps a silly question, but why maintain patches ? Why not compile a
new version and discard all the patches ? Patches are a messy manner to
maintain programmes.

> KVM was not chosen over Xen so much as KVM was a much less expensive
> hypervisor to support. As for it being mature or not; Well, put on your
> kevlar pants because that is a matter of opinion.

Which is better on C5 and C6 ?

> As a follow-up, Xen dom0 support began getting into the mainline kernel
> at 2.6.33 (EL6 is based on 2.6.32). It is very likely that we will see
> Xen dom0 support returned in the next major release.

In about 4 or 5 years ??? :-)

Regards,

Paul.


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Old 09-07-2011, 02:00 PM
Rudi Ahlers
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, Sep 7, 2011 at 3:51 PM, Digimer <linux@alteeve.com> wrote:
> On 09/07/2011 09:34 AM, Rudi Ahlers wrote:
>> Red Hat (and thus CentOS) has native XEN support but dropped XEN in
>> favor of KVM (which is not as mature yet) in RH 6.
>
> This deserves clarification...
>
> Red Hat is a business, and made a simple business decision. Maintaining
> Xen support would have meant maintaining a very large set of patches.
> They made the decision that the effort (and money) needed to maintain
> Xen outside of the mainline kernel was not worth it.
>

Well, I merely stated the facts of what the Red Hat Virtualization
package offers in the 2 different Red Hat releases, 5 & 6.


> KVM was not chosen over Xen so much as KVM was a much less expensive
> hypervisor to support. As for it being mature or not; Well, put on your
> kevlar pants because that is a matter of opinion.

I'm sure many people will argue against this perception since XEN has
been around much longer than KVM and, up to recently,"just worked"
every time. So the amount of effot they (or any other Linux distro)
had to put in to support it is minimal.
At the same time, in a different camp, there are those who speculate
that XEN was dropped since it's the defacto standard for Novell Suse /
OpenSuse and it's direct competition for Red Hat.

>
> As a follow-up, Xen dom0 support began getting into the mainline kernel
> at 2.6.33 (EL6 is based on 2.6.32). It is very likely that we will see
> Xen dom0 support returned in the next major release.

That would be nice and I'm sure Red Hat would gain some ground again
but if you look on the trend on the web many people stopped using Red
Hat (and derivatives of it, like CentOS) because of this very reason.


>
> --
> Digimer
> E-Mail: * * * * * * *digimer@alteeve.com
> Freenode handle: * * digimer
> Papers and Projects: http://alteeve.com
> Node Assassin: * * * http://nodeassassin.org
> "At what point did we forget that the Space Shuttle was, essentially,
> a program that strapped human beings to an explosion and tried to stab
> through the sky with fire and math?"
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>



--
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532
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Old 09-07-2011, 02:03 PM
John Hodrien
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, 7 Sep 2011, Always Learning wrote:

>
> On Wed, 2011-09-07 at 09:51 -0400, Digimer wrote:
>
>> Red Hat is a business, and made a simple business decision. Maintaining
>> Xen support would have meant maintaining a very large set of patches.
>> They made the decision that the effort (and money) needed to maintain
>> Xen outside of the mainline kernel was not worth it.
>
> Perhaps a silly question, but why maintain patches ? Why not compile a
> new version and discard all the patches ? Patches are a messy manner to
> maintain programmes.

That's fine if you just want to jump ship to a new version. But what if the
new version breaks some things, or changes behaviour in a way you don't want,
or removes a feature. Your choice effectively becomes do I back port things I
want to an old version, or maintain patches that takes current back to the
state I want.

> Which is better on C5 and C6 ?

That's a matter for google, and not necessarily a simple one to answer. As
was said, Xen was the standard option with C5, and KVM was with C6.

jh
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Old 09-07-2011, 02:05 PM
Digimer
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On 09/07/2011 09:57 AM, Always Learning wrote:
>
> On Wed, 2011-09-07 at 09:51 -0400, Digimer wrote:
>
>> Red Hat is a business, and made a simple business decision. Maintaining
>> Xen support would have meant maintaining a very large set of patches.
>> They made the decision that the effort (and money) needed to maintain
>> Xen outside of the mainline kernel was not worth it.
>
> Perhaps a silly question, but why maintain patches ? Why not compile a
> new version and discard all the patches ? Patches are a messy manner to
> maintain programmes.

That's the form they come from the community in. You'd have to ask the
devs for details.

>> KVM was not chosen over Xen so much as KVM was a much less expensive
>> hypervisor to support. As for it being mature or not; Well, put on your
>> kevlar pants because that is a matter of opinion.
>
> Which is better on C5 and C6 ?

For what? That is a loaded question.

For me, I use C5 + Xen when I am backing *nix VMs and c6 + KVM when
backing MS VMs as the PV drivers for windws are less than ideal.

>> As a follow-up, Xen dom0 support began getting into the mainline kernel
>> at 2.6.33 (EL6 is based on 2.6.32). It is very likely that we will see
>> Xen dom0 support returned in the next major release.
>
> In about 4 or 5 years ??? :-)

They tend to release a new x-stream release every three years. EL6 is a
year old, so I'd bet in two more years we will see EL7 and that both KVM
and Xen will be supported.

--
Digimer
E-Mail: digimer@alteeve.com
Freenode handle: digimer
Papers and Projects: http://alteeve.com
Node Assassin: http://nodeassassin.org
"At what point did we forget that the Space Shuttle was, essentially,
a program that strapped human beings to an explosion and tried to stab
through the sky with fire and math?"
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Old 09-07-2011, 02:12 PM
Always Learning
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, 2011-09-07 at 10:05 -0400, Digimer wrote:

> "At what point did we forget that the Space Shuttle was, essentially,
> a program that strapped human beings to an explosion and tried to stab
> through the sky with fire and math?"

And it worked. A tremendous and useful achievement now scrapped.



--
With best regards,

Paul.
England,
EU.


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Old 09-07-2011, 02:14 PM
Always Learning
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, 2011-09-07 at 15:03 +0100, John Hodrien wrote:

> On Wed, 7 Sep 2011, Always Learning wrote:
> >
> > Perhaps a silly question, but why maintain patches ? Why not compile a
> > new version and discard all the patches ? Patches are a messy manner to
> > maintain programmes.

> That's fine if you just want to jump ship to a new version. But what if the
> new version breaks some things, or changes behaviour in a way you don't want,
> or removes a feature.

If one compiled a 'new' version containing all those many existing
patches, would not that 'new' version simply work exactly as the old
version patched by countless alternations ?

Regards,

Paul.

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Old 09-07-2011, 02:18 PM
Always Learning
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

Thanks Guys for the helpful info.

Paul.


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Old 09-07-2011, 02:39 PM
John Hodrien
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, 7 Sep 2011, Always Learning wrote:

> On Wed, 2011-09-07 at 15:03 +0100, John Hodrien wrote:
>
>> On Wed, 7 Sep 2011, Always Learning wrote:
>>>
>>> Perhaps a silly question, but why maintain patches ? Why not compile a
>>> new version and discard all the patches ? Patches are a messy manner to
>>> maintain programmes.
>
>> That's fine if you just want to jump ship to a new version. But what if the
>> new version breaks some things, or changes behaviour in a way you don't want,
>> or removes a feature.
>
> If one compiled a 'new' version containing all those many existing
> patches, would not that 'new' version simply work exactly as the old
> version patched by countless alternations ?

If that's all you're doing, there's no pain in having the patches. But what
happens if you don't want *all* the patches?

jh
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Old 09-07-2011, 02:46 PM
Always Learning
 
Default Emulate RHEV On CentOS - A note on Xen v. KVM

On Wed, 2011-09-07 at 15:39 +0100, John Hodrien wrote:

> If that's all you're doing, there's no pain in having the patches.
> But what happens if you don't want *all* the patches?

A heavily patched programme is a messy compromise for system options
which could be handled by run-time configuration options ?

Paul.


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