Re: RPO 0 is good, but...
One thing that many people forget when promising RPO 0 is that it's a double-edged sword.
True RPO 0 means that no data you write can be lost, i.e. it is always written safely to the secondary data centre as well as the primary. Implicit in that is a requirement that your secondary data centre must always be available. If it goes down, or offline (even for maintenance) any writes at the primary won't get saved at the secondary until it comes back and catches up, so you don't have RPO 0 during that period.
To put it another way, if you need to guarantee RPO 0, you have to halt primary site operation if the DR site isn't available. It makes the secondary site & network a single point of failure. Is that really what customers want?
As the article points out, you can get nearly to RPO 0 with 3-site solutions where data is written synchronously to a backup in the metro area, where speed-of-light latency is manageable, and parallel asynchonous replication to a distant 3rd site. Lots of banking organizations are doing this to meet regulatory rules. There are some clever tricks you can play with database log shipping so that you don't actually need 3 full copies of all data, one at each site. Even so, I'd be very wary of any salesman who promised me permanent RPO 0. It's a good sign that he doesn't understand what he's selling.