[CentOS-virt] Best virtualization setup for Centos 5.2

Dennis J. dennisml at conversis.de
Wed Jan 21 19:00:24 UTC 2009

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only found some outdated and contested data on the web and virtualization 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.


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