[one-users] Creating new VM fails

[Javier Fontan]

Hello,


On May 22, 2009, at 8:07 PM, cmasmas cmasmas wrote:
> That was the problem. Thanks. I was requesting too much RAM. The  
> point is that each node has around 1.5 GB of free RAM. However,  
> opennebula detects about 100MB free on one noe, and 2 MB on the other.
>
>  HID NAME                      RVM   TCPU   FCPU   ACPU    TMEM     
> FMEM STAT
>    1 pc-GridLab00                0    200    199    200 2086912     
> 2048   on
>    3 pc-GridLab01                1    200    100    180 2069504    
> 24576   on
>
> Why is this?

This happens because Dom-0 of xen is taking the rest of the ram. You  
can decrease the ram it is taking form the command like using this  
command:

$ xm mem-max 0 256

It will change the amount of ram used by dom-0 to 256 Mb and the rest  
will be free for VM's.

If you want to set this parameter automatically on system startup / 
boot/grub/menu.lst can be modified so the kernel parameter looks  
something like this:

kernel          /xen-3.2.gz dom0_mem=256M

Just add the dom0_mem parameter, leave the path of your xen hypervisor  
as it is in your menu.lst.

> Another thing is that although one shows that the VM is running, xen  
> reveals that is really blocked.
>
>   ID     NAME STAT CPU     MEM        HOSTNAME        TIME
>   21 vm-examp runn   0  102400    pc-GridLab01 00 00:21:34


That is normal, blocked does not mean that the machine is stopped but  
that in the moment that you call xm command is not in the cpu  
executing instructions. It is like processes, you can have a bunch of  
processes running but only a number of them can be in the CPU  
executing instructions (the same as the number of cores you have in  
the computer). Also your machine is idling as you can see in the CPU  
value from monitoring so catching it doing something will be hard.

Bye

-- 
Javier Fontan, Grid & Virtualization Technology Engineer/Researcher
DSA Research Group: http://dsa-research.org
Globus GridWay Metascheduler: http://www.GridWay.org
OpenNebula Virtual Infrastructure Engine: http://www.OpenNebula.org