Live Migration Failed, Multipathd Service Not Running on Destination Host – Platform9

Problem

Instance live migration fails with below error in ostackhost.log of source host.

ERROR nova.compute.manager [-] [instance: "instance-id"] Pre live migration failed at "destination-host-uuid": RemoteError: Remote error: ProcessExecutionError Unexpected error while running command.
Command: multipathd show status
Exit code: 1
...
TRACE nova.compute.manager [instance: "instance-id"] Stderr: u'ux_socket_connect: Connection refused\n'

Environment

Platform9 Managed OpenStack - All Versions
multipathd
pf9-ostackhost

Cause

The pf9-ostackhost service on the source and the destination host is configured to use the multipath connection for volumes.
```
# less /opt/pf9/etc/nova/conf.d/nova_override.conf
..
volume_use_multipath = True
..
```
Once the live migration is initiated, a pre-live migration check is performed to confirm if the destination host is running the multipathd service.
If this pre-live migration check fails, the below command on the destination host will give the error mentioned in the problem section on source host.
```
$ multipathd show status
```

On the destination host, we can observe the error message with the live-migration request ID as below.

ERROR os_brick.initiator.linuxscsi [req-xxxxxxxxxxx user@domain service] multipathd is not running: exit code 1: ProcessExecutionError: Unexpected error while running command.

Check the status of multipathd service on the destination host.
```
$ systemctl status multipathd.service
```
This issue is most often observed if the multipathd service is not running on the destination host.

Resolution

Check multipath configuration in /etc/multipath.conf file on destination host.
If the configuration is correct, start the multipathd service if not running on the destination host.
```
$ systemctl start multipathd.service
```