KVM : Storage Migration2025/01/17

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/centos10.img

image: /var/kvm/images/centos10.img
file format: qcow2
virtual size: 20 GiB (21474836480 bytes)
disk size: 4.88 GiB
cluster_size: 65536
Format specific information:
    compat: 1.1
    compression type: zlib
    lazy refcounts: true
    refcount bits: 16
    corrupt: false
    extended l2: false
Child node '/file':
    filename: /var/kvm/images/centos10.img
    protocol type: file
    file length: 20 GiB (21478375424 bytes)
    disk size: 4.88 GiB
    Format specific information:
        extent size hint: 1048576

### 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/centos10.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 centos10

[root@kvm01 ~]#

virsh list

 Id   Name       State
--------------------------
 1    centos10   running

[root@kvm01 ~]#

virsh migrate --live --copy-storage-all centos10 qemu+ssh://kvm02.srv.world/system

[root@kvm01 ~]#

virsh list

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

# running virtual machines have been moved

### on another KVM host ###

[root@kvm02 ~]#

virsh list

 Id   Name       State
--------------------------
 2    centos10   running

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