RPO Zero Is a Network Question, Not a Backup Question — What “No Data Loss” Really Costs Between Two Sites
A customer rewrote their disaster-recovery requirement to “RPO ≈ 0 and the lowest possible RTO” and expected the backup line of the proposal to absorb it. It cannot. Zero data loss is only possible when the primary database refuses to confirm a write until a second site has it, and that decision is made by round-trip time and redo rate, not by any backup product. Here is the question that exposed the gap, why replication must never be sold as backup, the four numbers that decide synchronous versus asynchronous, and the honest commitment we ended up writing instead of “zero”.