...
Live migration for instances created on ephemeral storage
This procedure must be used only from/to hypervisor using LVM thin
Let's suppose that we want to migrate a VM with id dad2d364-3432-454d-a72d-910067e0187d from compute-02 to compute-04
First of all on the source hypervisor let's take a LV snapshotTo migrate an instance from a compute node to another one, you can use the "openstack server migrate" command with the '–block-migration' option, after having sourced the admin openrc script. E.g.:
| Code Block | ||
|---|---|---|
| ||
openstack server migrate[root@compute-02 ~]# lvcreate -s --live cld-np-14.cloud.pd.infn.it --block-migration e1914906-7e33-4d30-88f0-785130fdd85d |
This will live migrate the instance with uuid e1914906-7e33-4d30-88f0-785130fdd85d to the compute node cld-np-14.cloud.pd.infn.it.
name lvmnova.dad2d364-3432-454d-a72d-910067e0187d lvmvg/lvmnova
WARNING: Sum of all thin volume sizes (335.75 GiB) exceeds the size of thin pool lvmvg/pool00 and the size of whole volume group (167.88 GiB).
WARNING: You have not turned on protection against thin pools running out of space.
WARNING: Set activation/thin_pool_autoextend_threshold below 100 to trigger automatic extension of thin pools before they get full.
Logical volume "lvmnova.dad2d364-3432-454d-a72d-910067e0187d" created.
[root@compute-02 ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lvmnova lvmvg Vwi-aotz-- <167.88g pool00 6.11
lvmnova.dad2d364-3432-454d-a72d-910067e0187d lvmvg Vwi---tz-k <167.88g pool00 lvmnova
pool00 lvmvg twi-aotz-- <167.88g 6.14 11.04
[root@compute-02 ~]# |
Let's set the snapshot in read only mode:
| Code Block | ||
|---|---|---|
| ||
[root@compute-02 ~]# lvchange -p r lvmvg/lvmnova.dad2d364-3432-454d-a72d-910067e0187d
Logical volume lvmvg/lvmnova.dad2d364-3432-454d-a72d-910067e0187d changed.
[root@compute-02 ~]# |
Let's migrate the instance,using the "openstack server migrate" command with the '–block-migration' option, after having sourced the admin openrc script, i.e.In train the "–live" option is deprecated. You can use:
| Code Block | ||
|---|---|---|
| ||
[root@controller-01 ~]# openstack server migrate --os-compute-api-version 2.30 --live-migration --host compute-0304.cloud.pd.infn.it --block-migration dad2d364-3432-os454d-compute-api-version 2.79 92c413cb-d6f2-4103-9042-9e2e85257029a72d-910067e0187d [root@controller-01 ~]# |
The command doesn't work if source and target hypervisor aren't compatible. The error would be something like:
...
In this case, please find another compatible hypervisor, or you can use cold migration (i.e. the VM will be powered off during the migration)
If the block live migration for some reason didn't work and you have a "corrupted VM"
[root@controller-01 ~]# nova stop dad2d364-3432-454d-a72d-910067e0187d | grep comp
[root@controller-01 ~]#
| Code Block |
|---|
[root@compute-02 ~]# mkdir /mnt/snap [root@compute-02 ~]# mount /dev/lvmvg/lvmnova.dad2d364-3432-454d-a72d-910067e0187d /mnt/snap -o ro,nouuid,norecovery [root@compute-02 ~]# ll /mnt/snap/dad2d364-3432-454d-a72d-910067e0187d/ console.log disk disk.info [root@compute-02 ~]# scp /mnt/snap/dad2d364-3432-454d-a72d-910067e0187d/disk compute-04.cloud.pd.infn.it:/var/lib/nova/instances/dad2d364-3432-454d-a72d-910067e0187d The authenticity of host 'compute-04.cloud.pd.infn.it (192.168.60.89)' can't be established. ED25519 key fingerprint is SHA256:Fqq7jDeH98KxJ3J9QCFnBaWdiESy7gZ9+toHWU8i1jA. This host key is known by the following other names/addresses: ~/.ssh/known_hosts:1: compute-04 Are you sure you want to continue connecting (yes/no/[fingerprint])? yes Warning: Permanently added 'compute-04.cloud.pd.infn.it' (ED25519) to the list of known hosts. root@compute-04.cloud.pd.infn.it's password: disk [root@compute-02 ~]# umount /mnt/snap [root@compute-02 ~]# |
| Code Block |
|---|
[root@controller-01 ~]# nova start dad2d364-3432-454d-a72d-910067e0187d
Request to start server dad2d364-3432-454d-a72d-910067e0187d has been accepted.
[root@controller-01 ~]# |
Cold migration for instances created on ephemeral storage
...