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 I googled a bit but only found some outdated and contested data on the web and virtualization is a rather fast-moving field.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 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.
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
On 01/22/2009 09:31 AM, Kai Schaetzl wrote:
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.
same results here. 5.2 guest on 5.2 rocks. I have half a dozen installations (as in physical machines), one of them including several oracle instances as VMs [*], and not a single issue.
[*] no comment on oracle as VMs, please. it was not my decision.
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Dennis J. -
Farkas Levente -
Kai Schaetzl -
Manuel Wolfshant