[cinder-backup][ceph] replicate volume between sites

Hi,

I have two sites with OpenStack Victoria deployed by Kolla and Ceph Octopus deployed by cephadm. As what I know, either Swift (implemented by RADOSGW) or RBD is supported to be the backend of cinder-backup. My intention is to use one of those option to replicate Cinder volume from one site to another, based on RADOSGW multi-site support or RBD mirroring. I wonder if anyone has done this and could share some opinions, like pros, cons, which way is better for which case?

One specific thing I am not clear is that, how to import RBD volume into Cinder when it gets to another site. There used to be a way, but it's replicated.

Any comments is appreciated.

Thanks! Tony