Seems that Synciq will be the best solution for this case.  Thank you all for your comments.
Hi,  I need to move/copy particular folders (500TB) between clusters as fast as possible, do i have a chance to utilise infiniband interface/switches if i connect them to same IB switches -- (i can optionally use Synciq or not)  As far as i know more than one cluster is not recommended on same IB switch and IB interfaces are intra-cluster-only but may be someone find a workaround.
Moving data between two cluster