CentOS virt - Apr 2012 - XEN or KVM - performance/stability/security?

Hi all.

I am currently building a small test cloud based on Eucalyptus 2.0.3 and
CentOS 5.8 x64. I have a choice which hypervisor to use: KVM or XEN.
KVM is the default in CentOS 6 but I have read also many good things (for
example PV guest machines, isolation between Dom0 and DomU) about XEN.

Key factors from my opint of view are:
- stability (which one runs more smoothly on CentOS?)
- performance (XEN PV/HVM(with or without pv drivers) vs KVM HVM(with or
without pv drivers))
- security

Could you share your experience in these areas?

Best regards,
Rafal Radecki.

On 04/20/2012 01:59 PM, Rafa? Radecki wrote:
> I am currently building a small test cloud base..
...
> Could you share your experience in these areas?
try the centos-virt list ? Lots of people there ( including people who
write a lot of the code behind some of these things! )

-- 
Karanbir Singh
+44-207-0999389 | http://www.karan.org/ | twitter.com/kbsingh
ICQ: 2522219    | Yahoo IM: z00dax      | Gtalk: z00dax
GnuPG Key : http://www.karan.org/publickey.asc

On 4/20/2012 8:59 AM, Rafa? Radecki wrote:
> Hi all.
>
> I am currently building a small test cloud based on Eucalyptus 2.0.3 and
> CentOS 5.8 x64. I have a choice which hypervisor to use: KVM or XEN.
> KVM is the default in CentOS 6 but I have read also many good things (for
> example PV guest machines, isolation between Dom0 and DomU) about XEN.
>
> Key factors from my opint of view are:
> - stability (which one runs more smoothly on CentOS?)
> - performance (XEN PV/HVM(with or without pv drivers) vs KVM HVM(with or
> without pv drivers))
> - security
>
> Could you share your experience in these areas?
>
> Best regards,
> Rafal Radecki.
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
Xen all the way. That's just my opinion though.

Hi all.

I am currently building a small test cloud based on Eucalyptus 2.0.3 and
CentOS 5.8 x64. I have a choice which hypervisor to use: KVM or XEN.
KVM is the default in CentOS 6 but I have read also many good things (for
example PV guest machines, isolation between Dom0 and DomU) about XEN.

Key factors from my opint of view are:
- stability (which one runs more smoothly on CentOS?)
- performance (XEN PV/HVM(with or without pv drivers) vs KVM HVM(with or
without pv drivers))
- security

Could you share your experience in these areas?

Best regards,
Rafal Radecki.
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Hi,

KVM if used as it is will show very poor performance on CentOS5. To
achieve better results you need to update kernel to at least 2.6.32
and compile newer versions of libvirt and qemu. On CentOS6 all is fine
with KVM right out of the box.

Never used XEN so cannot compare.


Dmitry Cherkasov



2012/4/20 Rafa? Radecki <radecki.rafal at
gmail.com>:
> Hi all.
>
> I am currently building a small test cloud based on Eucalyptus 2.0.3 and
> CentOS 5.8 x64. I have a choice which hypervisor to use: KVM or XEN.
> KVM is the default in CentOS 6 but I have read also many good things (for
> example PV guest machines, isolation between Dom0 and DomU) about XEN.
>
> Key factors from my opint of view are:
> - stability (which one runs more smoothly on CentOS?)
> - performance (XEN PV/HVM(with or without pv drivers) vs KVM HVM(with or
> without pv drivers))
> - security
>
> Could you share your experience in these areas?
>
> Best regards,
> Rafal Radecki.
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

On 04/20/2012 02:15 PM, Rafa? Radecki wrote:
> Hi all.
> 
> I am currently building a small test cloud based on Eucalyptus 2.0.3 and
> CentOS 5.8 x64. I have a choice which hypervisor to use: KVM or XEN.
there are people who will argue both ways - and even add other options
to the mix and swear by them. End of the day, its going to be a case of
you having to put in a bit of time and eval the options based on your
own constraints and take it from there.

I use Xen quite a bit, I also use KVM - almost as much as Xen. And I
find they both solve their own problems in their own ways. I also use
VirtualBox and staring to get lxc into the mix. I have used vmware
products in the past.

-- 
Karanbir Singh
+44-207-0999389 | http://www.karan.org/ | twitter.com/kbsingh
ICQ: 2522219    | Yahoo IM: z00dax      | Gtalk: z00dax
GnuPG Key : http://www.karan.org/publickey.asc

A late reply, but hopefully a useful set of feedback for the archives:

On 04/20/2012 05:59 AM, Rafa? Radecki wrote:
> Key factors from my opint of view are:
> - stability (which one runs more smoothly on CentOS?)
I found that xenconsoled could frequently crash in Xen dom0, and that 
guests would be unable to reboot until it was fixed.  I also found that 
paravirt CentOS domUs would not boot if they were updated before the 
dom0.  In short, Xen paravirt was very fragile and troublesome.  I never 
tested Xen with hardware virtualization.

I have had no such problems with KVM.  In my experience KVM is much more 
stable than Xen paravirtualization.  Xen HVM probably would suffer at 
least some of the same problems.
> - performance (XEN PV/HVM(with or without pv drivers) vs KVM HVM(with or
> without pv drivers))
PV drivers will make some difference, but the biggest performance 
difference you'll see is probably the difference between file-backed VMs 
and LVM-backed VMs.  File-backed VMs are extremely slow.  Whichever 
system you choose, use LVMs as the backing for your guests.
> - security
There have been bugs that allow guests to escalate privileges and access 
host resources, but they're relatively few.  I don't think there's a
significant difference between the two in this area.

Overall I advise the use of KVM.  It should be more stable, and has the 
advantage of Red Hat support.