CentOS 7
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KVM : Storage Migration
2018/05/19
 
This is the example to use Storage Migration function for Virtual Machines.
The different point of Storage Migration from Live Migration is that Storage Migration does not need a Storage server which has Virtual Machine images, when executing Storage Migration, Virtual Machine image on a KVM host is migrated on another KVM host like follows.
                          Storage Migration
                        <------------------->
                        
+----------------------+                     +----------------------+
|  [   KVM Host #1  ]  |10.0.0.21   10.0.0.22|  [  KVM Host #2   ]  |
|                      +---------------------+                      |
|   kvm01.srv.world    |                     |    kvm02.srv.world   |
+----------------------+                     +----------------------+

[1]
Configure 2 KVM Host Server and Create a Virtual Machine on a KVM Host.
2 KVM Host Servers need to be resolv hostname or IP address each other via DNS or local hosts file.
[2] Update QEMU on KVM Host.
[root@kvm01 ~]#
/usr/libexec/qemu-kvm -version

QEMU emulator version 1.5.3 (qemu-kvm-1.5.3-156.el7), Copyright (c) 2003-2008 Fabrice Bellard
[root@kvm01 ~]#
yum -y install centos-release-qemu-ev
# disable on default

[root@kvm01 ~]#
sed -i -e "s/enabled=1/enabled=0/g" /etc/yum.repos.d/CentOS-QEMU-EV.repo
# for this installing, [qemu-kvm] package is replaced to [qemu-kvm-ev] package

[root@kvm01 ~]#
yum --enablerepo=centos-qemu-ev -y install qemu-kvm-ev
[root@kvm01 ~]#
systemctl restart libvirtd

[root@kvm01 ~]#
/usr/libexec/qemu-kvm -version

QEMU emulator version 2.10.0(qemu-kvm-ev-2.10.0-21.el7_5.2.1)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
[3] On KVM Hosts, if Firewalld is running, allow ports.
[root@kvm01 ~]#
firewall-cmd --add-service={libvirt,libvirt-tls} --permanent

[root@kvm01 ~]#
firewall-cmd --add-port=49152-49215/tcp --permanent

[root@kvm01 ~]#
firewall-cmd --reload

[4] Show the file size of a Virtual Machine image like follows on a KVM host and move to another KVM host, create a empty disk like follows.
# show the size of Virtual machine

root@kvm01:~#
ll /var/kvm/images

total 1344456
-rw-------. 1 root root 32217432064 May 19 23:44 centos7.img

### on another KVM host ###

# create a disk which is the same size of a Virtual Machine

root@kvm02:~#
qemu-img create -f qcow2 /var/kvm/images/centos7.img 32217432064

root@kvm02:~#
ll /var/kvm/images

total 196
-rw-r--r--. 1 root root 197120 May 20 00:19 centos7.img
[5] It's OK all, Run Storage Migration like follows.
root@kvm01:~#
virsh list

 Id    Name                           State
----------------------------------------------------
 1     centos7                        running

root@kvm01:~#
virsh migrate --live --copy-storage-all centos7 qemu+ssh://10.0.0.22/system

root@10.0.0.22's password:
root@kvm01:~#
virsh list

 Id    Name             State
--------------------------------------
# just migrated
### on another KVM host ###

root@kvm02:~#
virsh list

 Id    Name                           State
----------------------------------------------------
 1     centos7                        running

# back to another host, it's OK to execute normal Live Migration

root@kvm02:~#
virsh migrate --live centos7 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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