RAID Levels Guide — RAID 0, 1, 5, 6, and 10 Explained

RAID (Redundant Array of Independent Disks) helps you balance performance, capacity, and resilience. This guide summarizes the most common levels so you can make a confident choice, then verify it with the RAID Calculator.

RAID 0 (Striping)

Splits data across all disks. It delivers maximum throughput and IOPS because every disk contributes to reads and writes. There is no redundancy. If one disk fails, the entire array fails.

  • Pros: peak speed, 100% capacity.
  • Cons: zero fault tolerance.
  • Use cases: scratch space, temporary renders, non-critical workloads.

RAID 1 (Mirroring)

Duplicates identical data to a mirror disk. Reads can be fast. Writes go to both disks. Efficiency is 50%, but recovery is straightforward.

  • Pros: simple, resilient to single-disk failure.
  • Cons: halves capacity.
  • Use cases: boot volumes, small business servers, low-capacity critical data.

RAID 5 (Striping with Single Parity)

Stripes data plus parity across all disks. Needs three or more disks. Usable capacity ≈ (N − 1) × disk size. Rebuilds stress remaining disks, so plan for monitoring and backups.

  • Pros: good efficiency, single-disk fault tolerance.
  • Cons: write penalty, risky rebuild windows on large HDDs.
  • Use cases: balanced NAS arrays with 4–8 drives.

RAID 6 (Striping with Dual Parity)

Similar to RAID 5, but with two parity blocks. Needs four or more disks. Usable capacity ≈ (N − 2) × disk size. Safer on big arrays because it survives two failures.

  • Pros: two-disk fault tolerance.
  • Cons: more write overhead than RAID 5.
  • Use cases: large HDD arrays where rebuilds take many hours or days.

RAID 10 (Mirrored Stripes)

Stripes across mirrored pairs. Requires an even number of disks. Delivers strong IOPS and good resilience. Efficiency is roughly 50%.

  • Pros: excellent performance and resilience.
  • Cons: higher cost per usable TB.
  • Use cases: databases, VMs, mixed read/write workloads.
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