As the number of iSCSI or Fibre Channel LUNs or targets used by an Oracle VM Server is increased, the memory consumption increases on the server. This is normal, as more memory is required by dom0 to connect to each LUN or target. Therefore, if you intend to add a large number of LUNs to a server, you must allocate an appropriate amount of physical memory to the server to handle this, and the additional memory must be assigned to dom0 for use. Typically this should be around 1 MB per LUN on top of the memory allocated to run dom0. See Changing the Memory Size of the Management Domain for information on how to change the dom0 memory allocation.

Memory is assigned to dom0 within the grub configuration on the server. If you are using UEFI boot, the grub configuration file is located at /boot/efi/EFI/redhat/grub.cfg, otherwise the grub configuration file is located at /boot/grub2/grub.cfg. Edit the line starting with 'multiboot2 /xen.gz' and append the required boot parameters. For example, you may adjust the value for the dom0_mem parameter as shown in the following line of the configuration:

multiboot2 /xen.gz dom0_mem=max:6144M allowsuperpage dom0_vcpus_pin dom0_max_vcpus=20 
placeholder ${xen_rm_opts}

On servers running an earlier release of the current Oracle VM Server software,an earlier version of grub may still be in use. In this case the same result can be achieved by editing the /boot/grub/grub.conf file on the server and ammending the dom0_mem parameter in the line starting with 'kernel /xen.gz', as shown in the following line of the configuration:

kernel /xen.gz console=com1,vga com1=38400,8n1 dom0_mem=6144M allowsuperpage

Ideally this should be allocated at installation so that the dom0 grub configuration is updated automatically. Otherwise, you may need to adjust the grub configuration yourself.

Insufficient memory to support the number of LUNs on an Oracle VM Server results in out-of-memory (oom) kills and server instability.

Bug 17614799