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Nova

Nested virtualisation​

AMD​

echo "options kvm-amd nested=y" | sudo tee /etc/modprobe.d/kvm-nested-virtualization.conf
sudo modprobe -r kvm_amd
sudo modprobe kvm_amd
cat /sys/module/kvm_amd/parameters/nested
Y
docker restart nova_libvirt

Intel​

echo "options kvm-intel nested=y" | sudo tee /etc/modprobe.d/kvm-nested-virtualization.conf
sudo modprobe -r kvm_intel
sudo modprobe kvm_intel
cat /sys/module/kvm_intel/parameters/nested
Y
docker restart nova_libvirt

Reserve compute node resources​

How many resources you want to reserve on a compute node depends very much on which additional services are running on the compute node.

Host memory​

environments/kolla/files/overlays/nova/nova-compute.conf
[DEFAULT]
reserved_host_memory_mb = 32768

Host CPUs​

environments/kolla/files/overlays/nova/nova-compute.conf
[DEFAULT]
reserved_host_cpus = 4

Local SSD storage​

In this example, a local SSD is provided for use on compute node testbed-node-0. By default, Nova accesses the local storage on a file basis.

It is also possible to work with logical volumes instead. However, this is not recommended or supported by OSISM. More details in the Nova Configuration Guide.

On the compute node, the local SSD to be used is formatted with a file system of your choice and mounted to /var/lib/nova. When using more than one local SSD, a software RAID 1 should be used It is recommended to automate the creation of the file system and the creation of the mount point with a custom playbook.

A nova.conf configuration file is created as an overlay file for the compute node testbed-node-0. The name of the directory must match the name of the host in the inventory. If the compute node has a file with the name testbed-node-0.yml in the host_vars directory in the inventory, then the name of the directory in the overlays is testbed-node-0 accordingly. If the file name there were testbed-node-0.testbed.osism.xyz.yml then the name of the directory would be testbed-node-0.testbed.osism.xyz.

environments/kolla/files/overlays/nova/testbed-node-0/nova.conf
[libvirt]
images_type = raw

[glance]
enable_rbd_download = true

As Ceph is still used as the storage backend for Glance and Cinder, the image type is set to raw. To allow to download and cache images from Ceph via rbd rather than the Glance API via http enable_rbd_download is set to true.

Parameters must also be added in the inventory. This differs depending on the OSISM version used.

Up to OSISM 6 it looks like this:

In the inventory, the parameter nova_instance_datadir_volume is added in the section for the kolla environment.

inventory/host_vars/testbed-node-0.yml
##########################################################
# kolla

nova_instance_datadir_volume: /var/lib/nova

Starting with OSISM 7, it looks like this:

In the inventory, the parameters nova_instance_datadir_volume and nova_backend, are added in the section for the kolla environment.

inventory/host_vars/testbed-node-0.yml
##########################################################
# kolla

nova_instance_datadir_volume: /var/lib/nova
nova_backend: default

It is currently not possible to completely deactivate the Ceph integration with Nova. So if you have all compute nodes with local storage, you still have to do the Ceph integration for Nova itself and convert each compute node specifically to local storage. If this is not done, errors will occur when deploying Nova.