{{tag>[kvm migrate]}}

=====KVM Migrate VM to other host=====

===Prerequisites===
  * Restart VM on source host to be sure reboot is successful before the change.

===Migration iSCSI LV to image===
Example migration from iSCSI backed storage host to other host with local LVM based storage.

  * List the storage device, here 'vmns2'. <code>multipath -ll vmns2
vmns2 (3600140548f12334da9fed3985da3d6df) dm-14 SYNOLOGY,iSCSI Storage
size=64G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 6:0:0:17 sdo  8:224  active ready running
  `- 7:0:0:17 sdaf 65:240 active ready running</code>
  * Shutdown the VM. <code>virsh shutdown ns2</code>
  * Create compressed image from storage. I used 'pv' to show progress.<code>fdisk -l /dev/mapper/vmns2
    Disk /dev/mapper/vmns2: 68.7 GB, 68719476736 bytes

dd if=/dev/mapper/vmns2 bs=1M | pv -s 68719476736 | gzip -c > /var/tmp/ns2-disk-backup.img.gz</code>
  * Or use SSH direct: <code>dd if=/dev/mapper/vmdesktop bs=1M | pv -s 17179869184 | gzip -c | ssh -c arcfour benst@kvm1 'cat - > /var/tmp/desktop-disk-image.gz'</code>
  * Meanwhile... dump the xml. <code>virsh dumpxml ns2 > /tmp/ns2.xml</code>
  * Copy ns2.xml to new host and import. Edit file to change name / storage device etc... <code>virsh define /tmp/ns2.xml</code>
  * Create storage, same size as other host. <code>lvcreate -L 64G -n vmns2 vg_kvm1</code>
  * Copy image to new host, dd image to storage device. <code>gunzip -c ns2-disk-backup.img.gz | pv -s 68719476736 | dd of=/dev/vg_kvm1/vmns2 bs=1M
  64GB 0:14:05 [77.5MB/s] [================================>] 100%

134217728+0 records in
134217728+0 records out
68719476736 bytes (69 GB) copied, 851.545 s, 80.7 MB/s</code>
  * Start vm on new host. <code>virsh start vmns2</code>
  * Disable autostart on old host. <code>virsh autostart --disable ns2</code>
  * Enable autostart on new host. <code>virsh autostart vmns2</code>
  * Clean up vm and storage on old host / NAS.
===LV to qcow2 image===
  * Use qemu-img to convert from an lvm to qcow2 format <code>qemu-img convert -O qcow2 /dev/vg_name/lv_name/ /var/lib/libvirt/images/image_name.qcow2</code>
  * If you want the image compressed add '-c' right after the word convert.
  * Edit the xml for the image <code>virsh edit image_name</code>
  * Modify the disk stanza, adding a type to the driver line; on the source line change 'dev' to 'file' and modify the path: <code>driver name='qemu' type='qcow2'
source file='/var/lib/libvirt/images/image_name.qcow2'</code>
  * Shrink the file <code>qemu-img convert -c -O qcow2 source.qcow2 shrunk.qcow2</code>