Is SnapMirror up to the job of keeping an almost real-time remote replica, i.e. snap every minute if the networks up to it? Are there any operational issues around this stuff?
This one I can answer. Keep in mind that SnapMirror is not targeted to be a "almost real-time" remote replica. Its performance depends greatly on network, load, filesystem size etc. I wouldn't expect it to be a real-time style replica. If the networks are up to it you can get 24M/sec over the wire. Snapshots are created for each transfer which also take time.
So figure out how much data changes per minute how fast your networks are and how much load you are planning on and you start to see how fast the updates can happen. I have seen situations where a per minute schedule can be achieved but I would lean more towards every 15 minutes or so but really it depends on your situation.
I think it is a great product (I am biased) but I want to make sure your expectations are set correctly.
Mike Federwisch Network Appliance