Re: [Xen-users] RHEL xen vs kvm

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Apr 29, 2010 at 11:03:55AM -0700, Grant McWilliams wrote:
>    On Thu, Apr 29, 2010 at 9:53 AM, Pasi KÃârkkÃâinen <[1]pasik@xxxxxx>
>    wrote:
> 
>      On Wed, Apr 21, 2010 at 11:42:31PM -0700, Grant McWilliams wrote:
>      > Ã  Ã On Wed, Apr 21, 2010 at 7:26 PM, Jeff Sturm
>      <[1][2]jeff.sturm@xxxxxxxxxx>
>      >
> 
>      Do you have some benchmarks to prove KVM being faster than Xen HVM?
> 
>    Yes, I do. I've been gathering statistics for quite a while because I'm
>    writing a white paper on Linux Virtualization Performance.
>    I'll need to dig them up after I get back from work. The difference is
>    enough to sway the decision if someone was only going to virtualize
>    Windows. If someone were to just use PV though Xen wins hands down.
> 

I'm really surprised if there is a big difference between Xen HVM vs. KVM.

What software versions did you use? 
What kind of hardware? 

I'm sure Citrix Xen guys want to see the results and comment if there's 
something to tweak :)


>    >
>    > Ã  Ã Here's my thoughts.
>    > Ã  Ã If I were primarily virtualizing Windows I'd use KVM.
> 
>      Why? Xen has both the GPLPV Windows drivers, and the binary WHQL Citrix
>      Windows
>      PV drivers available today.
> 
>    You'd think wouldn't you? I don't think it has to do with two drivers.
>

What are the reasons then? ;) 

 
> 
>      > Ã  Ã If I were primarily virtualizing Linux I'd use Xen.
>      > Ã  Ã If I was using a bunch of old 3.4 Ghz Dual Core Xeons (I am) I'd
>      use Xen.
>      > Ã  Ã If I was wanting to nest VMs I'd use AMD CPUs and KVM (for now).
>      >
> 
>      Xen also now has patches to supported Nested virtualization on both
>      Intel and AMD.
>      I bet this will end up in the Xen 4.1 development tree in upcoming
>      weeks.
> 
>    I will be looking forward to this indeed. I don't want to change my
>    platform just because I need one thing.
>    How is it going to support nesting on Intel? I was under the impression
>    that AMD was the one that supported
>    this in hardware.

See the patches posted to xen-devel last week by Intel.


> 
>      > Ã  Ã If I wanted the most pain free path to keeping my hypervisor
>      updated I'd
>      > Ã  Ã use KVM.
>      > Ã  Ã If I was doing desktop virtualization (local login, not network
>      logins)
>      > Ã  Ã I'd use KVM or VirtualBox
>      > Ã  Ã If I wanted the most tried and true enterprise hypervisor out
>      there and
>      > Ã  Ã didn't want to use VMWARE then I'd use Xen. Citrix Xenserver,
>      VirtualIron,
>      > Ã  Ã Sun SVM (one flavor), Oracle Virtual Machine and Amazon EC2 are
>      all based
>      > Ã  Ã on Xen.
>      > Ã  Ã It might look like I lean toward KVM from this list but I still
>      prefer Xen
>      > Ã  Ã in most cases because of category 2.
>      >
> 
>      There are a lot of options for Xen dom0 kernel nowadays.. although extra
>      patching
>      or fetching the git tree is still needed.
> 
>    Lots of options? You mean like compiling your own kernel? Pain free means
>    running your distribution the way it came. I predict in the coming years
>    we'll have two options - running XCP or running XenServer. I'm not sure
>    how well either put out security patches.
>

Yeah, XCP or XenServer is an easy solution if you don't want to buid your
own platform.

-- Pasi


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