Definition
Redundant Array of Independent Disks
RAID combines multiple physical hard disk drives into a single logical unit to improve performance and reliability (fault tolerance).
Objectives
Performance
Data read/written in parallel across multiple disks (striping), significantly increasing throughput.
Reliability
Data duplicated or stored with parity information (mirroring or parity), allowing survival of one or more drive failures.
RAID Levels
RAID 0 (Striping)
Data split across disks. High performance, but no redundancy — one disk failure loses all data.
RAID 1 (Mirroring)
Data duplicated on two or more disks. High reliability, but expensive in storage capacity.
RAID 5 (Distributed Parity)
Data and parity striped across three or more disks. Balance of performance, capacity, and fault tolerance.