Comment 50 for bug 1806156

I agree to what iain MacDonnell (imacdonn) explained in the ticket description.

The online data migration seems to be ambiguous. One side, it is supposed to complete when cinder service is not running, on the other side, it needs a RPC response to know the capabilities of the cinder hosts. So as Iain said, the migration is partly designed fundamentally flawed.

The workaround could be this patch https://bugs.launchpad.net/cinder/+bug/1837703
There is NO need to do data online migration since Rocky, Stein and Train.