replication
termKeeping copies of data on more than one machine, so the loss of one does not lose the data.
The whole subject is the word 'when'. Synchronous replication confirms a write only after the copy has it, which costs latency proportional to distance and guarantees no loss; asynchronous confirms immediately and accepts that a failure loses whatever had not shipped. That choice is the recovery point objective expressed in engineering, and it cannot be avoided - a system that has not chosen has chosen asynchronous by default.
Also known as: mirroring