Not really that I know of, I've seen a few scripts thrown around, but I can't think of anything I can link you at the moment...

A lot of the time what I see is people do just copy some subset of data from cluster A to disk on a migration host, then uploading the downloaded data to cluster B, over and over again until everything is in cluster B.

You could try that:

https://ask.openstack.org/en/question/3857/is-there-any-scripts-available-to-automate-swift-uploading/ (https://ask.openstack.org/en/question...)