[CentOS-virt] Xen/VMWare Server comparison and "best Xen practices"?

Daniel de Kok danieldk at pobox.com
Mon Oct 15 12:45:22 UTC 2007

On Mon, 2007-10-15 at 13:32 +0200, Kai Schaetzl wrote:
> I'm wondering what others who have already used the Xen kernel for DomUs 
> and the (free) VMWare Server can say about the comparison in actual 
> day-to-day operation. I've only started playing with Xen on CentOS 5 and 
> I've been running VMWare Server only on Win2k3 servers so far, so I'm 
> missing direct comparibility.

It depends on what you want to run as a domU. Paravirtualization is very
fast (e.g. for running domU CentOS 4/5 kernels). On the other hand, some
devices are very slow if you use Xen HVM for running systems that do not
have a kernel that functions as a Xen domU. As long as we don't have
paravirtualized network/display drivers for those systems,
network/graphic performance will not be very good.

So, what do you plan to run as a virtual machine?

> I found that when I close the VM console that drops to 2-3%, so that 
> python process is obviously related to the VM console. The interesting 
> thing is that when I then reopen the console from the VM manager it keeps 
> going at about 3% and doesn't go up to the earlier 9%. But it still 
> zigzags between 3 and 11% then. All the figures have been taken from the 
> VM manager. The %us count in top seems to stay at 3% all the time.

Did you try to connect to the VM virtual framebuffer with vncviewer,
rather than virt-manager? What loads do you get then?

> I wonder if this problem might happen because I use the option of not 
> allocating all space in the filesystem file right-away. I also wonder if 
> performance might be better if it wouldn't need to grow.

I have never seen this problem on production machines. But I don't use
virt-manager, so I am not sure at what point it rewrites the domain
configuration files after the installation.

-- Daniel

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