[one-users] A question about the utilization of VMs

[Steven Timm]

What hypervisor are you using? If you are using KVM then this
behavior is normal, KVM only actually occupies the amount of RAM
that the virtual machine is actually using at the time and
OpenNebula reports the usage accordingly.  this makes it possible
to overbook and put 16 2-GB KVM VM's on a machine that has less physical
RAM than that.

Steve Timm


On Wed, 23 Nov 2011, Adnan Pasic wrote:

> Hello guys,
I have a
problem with understand one specific behaviour and I hope that this community
might help me with it.
Anyway, I
am writing my diploma thesis using OpenNebula and so far it has done everything
I imagined and wanted it to do. I deploy VMs and utilize every one of them with
the tool ÿÿlookbusyÿÿ. On normal physical hosts, lookbusy works perfectly,
utilizing the CPU/Memory as I set it and doesnÿÿt stop the utilization until the
whole process is killed.
When I
utilize my VM, however, I noticed the VMs being utilized for approx. 2 minutes,
but afterwards I can see a falling trend of utilized memory on the physical
host. For instance, I utilize the memory of the VM by 2 GB ÿÿ thus, the physical
host shows the same utilization too. Nevertheless, after 2 minutes, the
utilization on the physical host starts decreasing and stops at about 500MB of
utilized memory, although the VM shows the whole time a full utilization of 2GB
!
Do you know
what could be the reason? Maybe it has something to do with the scheduler, or I
donÿÿt know?
Please help
me with this, as this is a crucial part of my diploma thesis and I got stuck!!!
 
Thanks in
advance.
Regards,
Adnan

-- 
------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
timm at fnal.gov  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Group Leader.
Lead of FermiCloud project.