CentOS virt - Jan 2009 - Best virtualization setup for Centos 5.2

Hi,
we are running Centos 5.2 on our servers for some time now and are really 
happy with it. Now I'm investigating the best way to setup virtual machines
in order to streamline our infrastructure. The setup I'm aiming for is 
Centos 5.2 guests on Centos 5.2 host. The physical systems are going to be 
2xquad core Xeons and the VMs are probably going to be 1 or 2 vCPUs with 1 
or 2 gb of ram for each guest. I plan to migrate a number of vmware 
instances on such a setup so I'm wondering what I can expect 
performance-wise when switching to either Xen or KVM.

As far as I understand is Xen is the "official" supported solution
with
Centos 5. I downloaded the KVM kernel module and some tools from a repo at 
lfarkas.org (unfortunately the new virt-manager there cannot be installed 
due to depency issues) to experiment with KVM which works so far but gives 
me weird results. Doing a "hdparm -t" on the host system consistently
gives
me a result of about 70MB/sec yet in a KVM guest I get results ranging from 
40MB/sec to 125MB/sec on each run.

Also the Centos kernel does not support the virtio drivers needed for KVM 
paravirtualization so I'm wondering how fast hardware assisted block-io 
under KVM is compared to the performance of the paravirtualized Xen driver 
and to vmware esx based guests.

Are there any current performance benchmarks out there? I googled a bit but 
only found some outdated and contested data on the web and virtualization 
is a rather fast-moving field.

Regards,
   Dennis

Dennis,

----- "Dennis J." <dennisml at conversis.de>
wrote:
> Now I'm investigating the best way to setup virtual machines in 
> order to streamline our infrastructure. The setup I'm aiming for is
> Centos 5.2 guests on Centos 5.2 host.
Since you are wanting to do Linux on Linux virtualization, I thought I'd
mention OpenVZ.  Check out the CentOS OpenVZ HOWTO on the wiki.  If you have any
questions about using OpenVZ on CentOS, just ask.

http://wiki.centos.org/HowTos/Virtualization/OpenVZ

TYL,
-- 
Scott Dowdle
704 Church Street
Belgrade, MT 59714
(406)388-0827 [home]
(406)994-3931 [work]

Dennis J. wrote:
> Hi,
> we are running Centos 5.2 on our servers for some time now and are really 
> happy with it. Now I'm investigating the best way to setup virtual
machines
> in order to streamline our infrastructure. The setup I'm aiming for is 
> Centos 5.2 guests on Centos 5.2 host. The physical systems are going to be 
> 2xquad core Xeons and the VMs are probably going to be 1 or 2 vCPUs with 1 
> or 2 gb of ram for each guest. I plan to migrate a number of vmware 
> instances on such a setup so I'm wondering what I can expect 
> performance-wise when switching to either Xen or KVM.
> 
> As far as I understand is Xen is the "official" supported
solution with
> Centos 5. I downloaded the KVM kernel module and some tools from a repo at 
> lfarkas.org (unfortunately the new virt-manager there cannot be installed 
> due to depency issues) to experiment with KVM which works so far but gives 
> me weird results. Doing a "hdparm -t" on the host system
consistently gives
> me a result of about 70MB/sec yet in a KVM guest I get results ranging from
> 40MB/sec to 125MB/sec on each run.
> 
> Also the Centos kernel does not support the virtio drivers needed for KVM 
> paravirtualization so I'm wondering how fast hardware assisted block-io
> under KVM is compared to the performance of the paravirtualized Xen driver 
> and to vmware esx based guests.
> 
> Are there any current performance benchmarks out there? I googled a bit but
> only found some outdated and contested data on the web and virtualization 
> is a rather fast-moving field.
may be worth waiting a little bit more, since:
- rhel 5.3 released, so in a few weeks we'll have centos 5.3 and
according rhel's annoncement it has some virtio_net support,
- there'll be a new virt-manager and virtinst release in the near future
(according to a last week's mail) which contains rhel-5 fixes.

anyway imho xen is much more stable on rhel/centos-5 hosts then the
current kvm line. kvm will be usable on kernel-2.6.29 and since
rhel/centos-5  will be always 2.6.18 based we've towait for
rhel/centos-6 which won't be in this year:-( or you can use other distro
like fedora or ubuntu at least for host os.

-- 
  Levente                               "Si vis pacem para bellum!"

Dennis J. wrote on Wed, 21 Jan 2009 20:00:24 +0100:
> Doing a "hdparm -t" on the host system consistently gives 
> me a result of about 70MB/sec yet in a KVM guest I get results ranging from
> 40MB/sec to 125MB/sec on each run.
The higher results after the first run are from caching. Xen will give you 
just a little bit less than the host. We are using only Xen and are happy with 
it. If you want to use CentOS on CentOS, there's nothing that beats Xen. 
Absolutely stable, reliable and good performance.

Kai

-- 
Kai Sch?tzl, Berlin, Germany
Get your web at Conactive Internet Services: http://www.conactive.com

Sergej,

----- "Sergej Kandyla" <sk.paix at gmail.com>
wrote:
> I also looking for light weight virtualization solutions.
> OpenVZ seems very good, but only reason that stopped me is that openvz
> kernel is not officially supported by CentOS\RHEL.
> 
> What could you say about stability of OpenVZ ?
> 
> Afaik, OpenVZ kernel is based on RHEL/CentOS kernel, but what the
> difference between them?
> Is any RHEL stability patches also included in OpenVZ kernel ?
The OpenVZ Project currently has three stable kernel branches: 1) RHEL4 2.6.9
based, 2) RHEL5 2.6.18 based, and 3) vanilla 2.6.18.  They have a number of
development branches that may or may not make it to stable including 2.6.24
(used by Ubuntu), 2.6.26 (in the upcoming Debian 5.0), and 2.6.27.

Whenever Red Hat releases a kernel update they try to upgrade OpenVZ but the
porting effort and the QA testing efforts can take some time... and sometimes
Red Hat will come out with another kernel update before OpenVZ has released the
last one.  As a result, OpenVZ can at times lag behind the Red Hat kernel some. 
Of course they try to give more weight to serious security problems and released
a update to the vslice issue (a very serious security issue in a range of
mainline kernels a while ago) about the same time the CentOS project did... if I
remember correctly.

So far as stability goes, I haven't had any issues with their kernels so I
have found them to be very stable.

TYL,
-- 
Scott Dowdle
704 Church Street
Belgrade, MT 59714
(406)388-0827 [home]
(406)994-3931 [work]