Redundant is a weird word, because it has both a negative and a positive aspect: being made redundant means you lose your job, but the other aspect is far more interesting: Redundancy in technology means you use multiple things to back each other up, so the end result becomes more solid and fail-proof.
Techniques like that are as old as the Apollo program or even before, where they had three computers doing the same calculations, and the majority rule was what they would follow. A more recent example is in the movie 'Minority Report', where criminals are being caught before the crime: the three 'Pre-cogs' must be in unison, but sometimes they are not...
A more recent application of redundancy in everyday tech is the blockchain, a software construct that retains redundant copies of itself on every computer taking part in the network, to avoid tampering.