You can replicate data from a SnapMirror destination to another system using SnapMirror. Therefore, a system that is a destination for one SnapMirror relationship can act as the source for another SnapMirror relationship. This is useful when you need to copy data from one site to many sites.
Instead of replicating data from a single source to each of the destinations, you can replicate data from one destination to another destination, in a series. This is referred to as cascading.
Note: You can replicate data from a destination volume in the same way you replicate from a writable source volume.