What is RAID?

RAID stands for Redundant Array of Independent Disks. It's a method of combining multiple physical drives into one logical unit for improved performance, redundancy, or both.

• RAID 0 (Striping): Data split across drives. Fastest, but no protection — one drive fails, all data is lost.
• RAID 1 (Mirroring): Duplicates data on two or more drives. If one fails, the other keeps working. 50% usable capacity.
• RAID 5 (Striping + Parity): Requires 3+ drives. One drive's worth of space is used for parity. Protects against one failure.
• RAID 6 (Double Parity): Like RAID 5, but with two parity blocks. Requires 4+ drives. Survives two drive failures.
• RAID 10 (1+0): A stripe of mirrors. Combines speed of RAID 0 and redundancy of RAID 1. Needs an even number of drives.

Choosing the right RAID depends on your priorities: performance, redundancy, or usable capacity.

RAID Types (Reference)

RAID Levels Comparison Chart

Feature	RAID 0	RAID 1	RAID 1E	RAID 10	RAID 5	RAID 50	RAID 6	RAID 60
Min disks	2	2	3	4	3	6	4	8
Fault tolerance	❌ None	✅ 1 disk	✅ 1 disk	✅ 1 per mirror set	✅ 1 disk	✅ 1 disk	✅ 2 disks	✅ 2 disks
Disk overhead	None	50%	~50%	50%	1 disk	2 disks	2 disks	4 disks
Read speed	🚀 Fast	🚀 Fast	🚀 Fast	🚀 Fast	🔄 Moderate–Fast*	🔄 Moderate–Fast	🔄 Moderate	🔄 Moderate
Write speed	🚀 Fast	⚖️ Fair	⚖️ Fair	⚖️ Fair	🐢 Slower*	🐢 Slower	🐢 Slower	🐢 Slower
Hardware cost	💲 Low	💲💲 High (due to mirroring)	💲💲 High	💲💲 High	💲 High	💲💲 Very high	💲💲 Very high	💲💲 Very high

*Performance varies depending on hardware RAID controllers and caching capabilities.

---

RAID 50 (5+0)

Combines multiple RAID 5 arrays striped together. Requires at least 6 drives. Offers better performance than RAID 5 with some fault tolerance.

Stripe	RAID 5 Array	Data Layout
Stripe 1	Drives 1–3	Data1 | Data2 | Parity
Stripe 2	Drives 4–6	Data3 | Data4 | Parity

RAID 60 (6+0)

Like RAID 50, but uses RAID 6 arrays. Requires at least 8 drives. Offers greater fault tolerance (up to 2 drives per array).

Stripe	RAID 6 Array	Data Layout
Stripe 1	Drives 1–4	Data1 | Data2 | Parity1 | Parity2
Stripe 2	Drives 5–8	Data3 | Data4 | Parity1 | Parity2

RAID 2, 3, 4 (Rare)

• RAID 2: Uses Hamming code for error correction. Obsolete.
• RAID 3: Stripes data with a dedicated parity disk. Rare.
• RAID 4: Similar to RAID 5 but with a single dedicated parity disk. Rarely used.

Nested RAID Summary

RAID Level	Description	Minimum Drives
RAID 10	Mirror + Stripe. Fast and redundant.	4
RAID 01	Stripe + Mirror. Less resilient than RAID 10.	4
RAID 50	Stripe of RAID 5s. Balanced performance and redundancy.	6
RAID 60	Stripe of RAID 6s. Better fault tolerance.	8