RAID

RAID is a storage technology that combines multiple physical disks into a single logical unit to improve performance, reliability, and fault tolerance.

It is widely used in servers, databases, and enterprise storage systems to protect data and improve disk performance.

Why RAID is Used

• Improve storage performance
• Provide fault tolerance
• Increase storage capacity
• Prevent data loss when a disk fails

Basic RAID Architecture

Server
   │
RAID Controller
   │
 ┌───────┬───────┬───────┬───────┐
 Disk1   Disk2   Disk3   Disk4

The RAID controller manages how data is distributed across the disks.

Common RAID Levels

RAID 0 – Striping

Data is split across multiple disks to improve performance.

Disk1 → Data A
Disk2 → Data B
Disk3 → Data C

• High performance
• No redundancy
• If one disk fails, all data is lost

RAID 1 – Mirroring

Data is duplicated across two disks.

Disk1 → Data A
Disk2 → Data A (copy)

• High reliability
• Simple recovery
• Requires double storage

RAID 5 – Striping with Parity

Data and parity information are distributed across multiple disks.

Disk1 → Data
Disk2 → Data
Disk3 → Parity

• Good balance of performance and fault tolerance
• Can survive one disk failure

RAID 10 – Mirroring + Striping

RAID 10 combines RAID 1 and RAID 0.

• Very high performance
• High fault tolerance
• Used in high-performance databases

RAID Level Comparison

Real World Example

A database server may store critical data using RAID 10 to ensure both high performance and fault tolerance.

Example setup:

• Database server
• Multiple SSD disks
• RAID controller

Quick Summary