Tuesday, April 14, 2015

Calculate DOM0 memory size

When using Oracle VM server as a virtualization platform you will have to ensure that DOM0 has enough memory allocated to it. Dom0 is the initial domain started by the Xen hypervisor on boot. Dom0 is an abbrevation of "Domain 0" (sometimes written as "domain zero" or the "host domain"). Dom0 is a privileged domain that starts first and manages the DomU unprivileged domains.

To ensure the correct amount of memory is allocated to DOM0 Oracle propagates the below mentioned algorithm to be used:

dom0_mem = 502 + int(physical_mem * 0.0205)

As an example this would mean that a server with 2 GB of physical memory would need 543MB of memory allocated to DOM0. A server with 32 GB of physical memory would need 1173MB of memory allocated to DOM0..

To change the Dom0 memory allocation, edit the /boot/grub/grub.conf file on the Oracle VM Server and change the dom0_mem parameter, for example, to change the memory allocation to 1024 MB, edit the file to be:

kernel /xen.gz console=com1,vga com1=38400,8n1 dom0_mem=1024M
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