secondary storages will automatically replicate data from the primary storage. 
Replication is superior to back-ups because as long as secondaries are running,
secondary data is kept updated. In the event of a failure of a primary storage,
just reconfigure a secondary to be the primary, and it can begin handling
application requests. 
Features
    Primary/secondary replication
    Support for read-only secondary storages
    Service registration and discovery with ZooKeeper 
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