Definition
Redundant Array of Independent Disks
RAID (Redundant Array of Independent Disks) is a technology that combines multiple physical hard disk drives into a single logical unit to improve performance and reliability (fault tolerance).
Design Objectives
- Performance: Data can be read and written in parallel across multiple disks (striping), significantly increasing throughput.
- Reliability: Data is duplicated or stored with parity information across the disks (mirroring or parity), allowing the system to survive the failure of one or more physical drives.
Common RAID Levels
- RAID 0 (Striping): Data is split across disks. High performance, but no redundancy (if one disk fails, all data is lost).
- RAID 1 (Mirroring): Data is duplicated on two or more disks. High reliability, but expensive in terms of storage capacity.
- RAID 5 (Distributed Parity): Data and parity information are striped across three or more disks. Provides a balance of performance, capacity, and fault tolerance.