Configuring Migrations

Configure your DNS or /etc/hosts and ensure it is consistent across all hosts. Make sure that the three hosts can perform name resolution with each other. As a test, use the ping command to ping each host from one another.

$ ping HostA
$ ping HostB
$ ping HostC

Ensure that the UID and GID of your nova and libvirt users are identical between each of your servers. This ensures that the permissions on the NFS mount will work correctly.

Follow the instructions at the Ubuntu NFS HowTo to setup an NFS server on HostA, and NFS Clients on HostB and HostC.

Our aim is to export NOVA-INST-DIR/instances from HostA, and have it readable and writable by the nova user on HostB and HostC.

Using your knowledge from the Ubuntu documentation, configure the NFS server at HostA by adding a line to /etc/exports

NOVA-INST-DIR/instances HostA/255.255.0.0(rw,sync,fsid=0,no_root_squash)

Change the subnet mask (255.255.0.0) to the appropriate value to include the IP addresses of HostB and HostC. Then restart the NFS server.

$ /etc/init.d/nfs-kernel-server restart
$ /etc/init.d/idmapd restart

Set the 'execute/search' bit on your shared directory

On both compute nodes, make sure to enable the 'execute/search' bit to allow qemu to be able to use the images within the directories. On all hosts, execute the following command:

$ chmod o+x NOVA-INST-DIR/instances 

Configure NFS at HostB and HostC by adding below to /etc/fstab.

HostA:/ /NOVA-INST-DIR/instances nfs4 defaults 0 0

Then ensure that the exported directory can be mounted.

$ mount -a -v

Check that "NOVA-INST-DIR/instances/" directory can be seen at HostA

$ ls -ld NOVA-INST-DIR/instances/

drwxr-xr-x 2 nova nova 4096 2012-05-19 14:34 nova-install-dir/instances/
          

Perform the same check at HostB and HostC - paying special attention to the permissions (nova should be able to write)

$ ls -ld NOVA-INST-DIR/instances/

drwxr-xr-x 2 nova nova 4096 2012-05-07 14:34 nova-install-dir/instances/
          

$ df -k

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1            921514972   4180880 870523828   1% /
none                  16498340      1228  16497112   1% /dev
none                  16502856         0  16502856   0% /dev/shm
none                  16502856       368  16502488   1% /var/run
none                  16502856         0  16502856   0% /var/lock
none                  16502856         0  16502856   0% /lib/init/rw
HostA:        921515008 101921792 772783104  12% /var/lib/nova/instances  ( <--- this line is important.)

Update the libvirt configurations so that the calls can be made securely. These methods enable remote access over TCP and are not documented here, please consult your network administrator for assistance in deciding how to configure access.

Restart libvirt. After you run the command, ensure that libvirt is successfully restarted:

$ stop libvirt-bin && start libvirt-bin
$ ps -ef | grep libvirt

root 1145 1 0 Nov27 ? 00:00:03 /usr/sbin/libvirtd -d -l

Configure your firewall to allow libvirt to communicate between nodes.

Information about ports used with libvirt can be found at the libvirt documentation By default, libvirt listens on TCP port 16509 and an ephemeral TCP range from 49152 to 49261 is used for the KVM communications. As this guide has disabled libvirt auth, you should take good care that these ports are only open to hosts within your installation.

You can now configure options for live migration. In most cases, you do not need to configure any options. The following chart is for advanced usage only.