When placing HDFS replicas for water-quality archives, why do replication policies care about racks or failure domains?
Select an answer to reveal the explanation.
Short Explanation
Don’t put all spare tires in the same locked garage that floods. Replica placement spreads copies across racks or failure domains so one outage does not erase every copy of a water-quality block. Co-locating all replicas on one platter defeats that idea.
Full Explanation
HDFS replication policies place block replicas across failure domains such as racks so a single domain failure is less likely to destroy every copy. That intuition underpins durability design. Forcing all replicas onto one disk, pushing metadata into mobile apps, or inventing rack SKUs are not the durability rationale.