CentOS Stream 9
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KVM : Storage Migration
2022/01/20
 
This is the example to use Storage Migration feature for Virtual Machines.
The different point of Storage Migration from the Common Live Migration is that Storage Migration does not need a Storage server that 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  ]  |10.0.0.30   10.0.0.51|  [  KVM Host #2   ]  |
|                      +---------------------+                      |
|   kvm01.srv.world    |                     |    kvm02.srv.world   |
+----------------------+                     +----------------------+

[1]
Configure 2 KVM Host Server and Create a Virtual Machine on a KVM Host.
Configure DNS or hosts to resolve names or IP addresses normally, first.
[2] On KVM Hosts, if Firewalld is running, allow ports.
[root@kvm01 ~]#
firewall-cmd --add-service={libvirt,libvirt-tls}

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

[root@kvm01 ~]#
firewall-cmd --runtime-to-permanent

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

[root@kvm01 ~]#
qemu-img info /var/kvm/images/centos-st9.img

image: /var/kvm/images/centos-st9.img
file format: qcow2
virtual size: 20 GiB (21474836480 bytes)
disk size: 5.15 GiB
cluster_size: 65536
Format specific information:
    compat: 1.1
    compression type: zlib
    lazy refcounts: true
    refcount bits: 16
    corrupt: false
    extended l2: false

### on another KVM host ###

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

[root@kvm02 ~]#
qemu-img create -f qcow2 -o preallocation=falloc /var/kvm/images/centos-st9.img 21474836480

[4] That's OK, Run Storage Migration like follows.
For connection between KVM Hosts, they connects to others with SSH, so it had better to set SSH key-pair with root account before running live migration.
[root@kvm01 ~]#
virsh start centos-st9

[root@kvm01 ~]#
virsh list

 Id   Name         State
----------------------------
 1    centos-st9   running

[root@kvm01 ~]#
virsh migrate --live --copy-storage-all centos-st9 qemu+ssh://kvm02.srv.world/system

[root@kvm01 ~]#
virsh list

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

# just migrated
### on another KVM host ###

[root@kvm02 ~]#
virsh list

 Id   Name         State
----------------------------
 1    centos-st9   running

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