Storage Redundancy and RAID Questions

Principles and practical trade offs for protecting data at the storage layer. Explain common redundancy schemes including striping, mirroring, and parity, and describe RAID levels such as zero, one, five, and six. Discuss how parity or replication is used to reconstruct lost data, the cost and performance impacts of different levels, rebuild times and degraded mode behavior, and higher level alternatives such as erasure coding and distributed replication for large scale systems. Candidates should be able to recommend redundancy approaches given recovery time and recovery point objectives, cost constraints, and workload patterns.