KVM : Live Migration2018/05/18

This is the example to use Live Migration function for Virtual Machines.

This requires 2 KVM host server and a storage server like follows.
Please set DNS or hosts to resolve names or IP addresses normally, first.

                      +----------------------+
                      |   [  NFS Servver  ]  |
                      |     nfs.srv.world    |
                      |                      |
                      +-----------+----------+
                                  |10.0.0.35
                                  |
+----------------------+          |          +----------------------+
|  [   KVM Host #1  ]  |10.0.0.21 | 10.0.0.22|  [  KVM Host #2   ]  |
|                      +----------+----------+                      |
|   kvm01.srv.world    |                     |    kvm02.srv.world   |
+----------------------+                     +----------------------+

[1]	Configure Storage server which has virtual machine images. For Storage server, it's OK to use NFS, iSCSI, GlusterFS and so on. This example uses NFS Storage server.
[2]	Configure 2 KVM host server and mount a directory provided from Storage server on the same mount point on both KVM server. This example mounts on [/var/kvm/images]. And also, 2 servers need to be resolv hostname or IP address each other via DNS or local hosts file.
[3]	Create a Virtual Machine on a KVM Host and migrate it to another KVM Host like follows.

# edit settings of VM you'd like to migrate

root@kvm01:~#

virsh edit ubuntu1804

 <disk type='file' device='disk'>
      # add: sepcify disk cache mode [none]
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/var/kvm/images/ubuntu1804.img'/>

root@kvm01:~#

virsh start ubuntu1804

root@kvm01:~#

virsh list

 Id    Name                           State
----------------------------------------------------
 1     ubuntu1804                     running

root@kvm01:~#

virsh migrate --live ubuntu1804 qemu+ssh://10.0.0.22/system

root@10.0.0.22's password:

# root password

root@kvm01:~#

virsh list

 Id    Name             State
--------------------------------------

# just migrated

### on another KVM Host ###

root@kvm02:~#

virsh list

 Id    Name                           State
----------------------------------------------------
 1     ubuntu1804                     running

# back to the KVM Host again like follows

root@kvm02:~#

virsh migrate --live ubuntu1804 qemu+ssh://10.0.0.21/system

root@10.0.0.21's password:

root@kvm02:~#

virsh list

 Id    Name             State
--------------------------------------

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