Quick RAID capacity calculator

Enter number of identical disks and size in TB – we'll estimate usable capacity for the most common RAID levels.

Why RAID matters

RAID (Redundant Array of Independent Disks) combines multiple drives into one logical group to improve performance and resilience. Choosing the right level helps you balance capacity, speed, and fault tolerance.

Essentials in a minute

• Striping: data is split across disks to increase throughput.
• Mirroring: data is duplicated for redundancy.
• Parity: extra information to recover from disk failures.
• Usable capacity: real space available after RAID overhead.

Common RAID levels

RAID 0 — striping only

• Usable: N × S
• Resilience: none (any disk failure loses data)
• Use: temporary/non‑critical workloads

RAID 1 — mirroring

• Usable: S (from two disks of size S)
• Resilience: one disk may fail
• Use: OS/boot volumes, simple HA pairs

RAID 5 — parity

• Usable: (N − 1) × S (min. 3 disks)
• Resilience: one disk may fail
• Use: balanced capacity + redundancy

RAID 6 — dual parity

• Usable: (N − 2) × S (min. 4 disks)
• Resilience: two disks may fail
• Use: large arrays, slow rebuild media

RAID 10 — mirrors + striping

• Usable: (N / 2) × S (even number of disks)
• Resilience: multiple failures tolerated if each mirror keeps one disk
• Use: high‑IOPS databases, virtualization, low latency

Quick selection guide

• Top performance + resilience: RAID 10
• Balanced capacity + safety: RAID 5 (small) or RAID 6 (large)
• Simple OS protection: RAID 1
• Performance only: RAID 0 (understand the risk)

Capacity cheat sheet

Level	Disks (N)	Disk size (S)	Usable	Failures
RAID 0	N	S	N × S	0
RAID 1	2	S	S	1
RAID 5	≥ 3	S	(N − 1) × S	1
RAID 6	≥ 4	S	(N − 2) × S	2
RAID 10	even ≥ 4	S	(N / 2) × S	per mirror

Example: 8 × 4 TB

• RAID 5 → 28 TB
• RAID 6 → 24 TB
• RAID 10 → 16 TB

If you need help sizing IOPS/throughput or rebuild windows, contact our team — we can model it for your workload.