RAID Calculator

What Is RAID?

RAID (Redundant Array of Independent Disks) combines multiple drives into one logical volume. Different RAID levels trade off usable capacity, read/write performance, and fault tolerance. Use this calculator to compare RAID 0, 1, 5, 6, and 10 before building a NAS or server array.

Usable Capacity Formula

Raw capacity is disk count times disk size. Usable capacity depends on the RAID level because parity and mirroring reserve space for redundancy.

$$C_{\text{usable}} = C_{\text{raw}} - C_{\text{overhead}}$$

Example: five 2 TB disks in RAID 5 keep four disks of data and one parity disk, so usable capacity is 8 TB (80% utilization).

RAID Level Comparison

RAID 0 stripes data for maximum speed but no redundancy.
RAID 1 mirrors disks for high reliability with 50% capacity on two drives.
RAID 5 stripes with single parity; one disk can fail.
RAID 6 adds double parity; two disks can fail.
RAID 10 mirrors then stripes for strong performance and one-disk failure per mirror pair.

Related tools: Data Size Converter and Download Time Calculator.

Frequently Asked Questions

How many disks do I need for RAID 5?

RAID 5 requires at least three disks. One disk worth of capacity is used for parity, so usable space is (n - 1) times the size of one disk.

Is RAID a backup?

No. RAID protects against drive failure, not accidental deletion, ransomware, or site disasters. Always keep separate backups.

Which RAID level is fastest?

RAID 0 offers the highest theoretical read and write speed because data is striped across all disks with no parity overhead.

What is capacity utilization?

Capacity utilization is usable capacity divided by raw capacity, expressed as a percentage. RAID 1 on two equal disks is 50% utilization.

Does RAID 10 need an even number of disks?

Yes. RAID 10 pairs mirrored sets, so the disk count must be even and at least four.

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What Is RAID?

Usable Capacity Formula

RAID Level Comparison

Frequently Asked Questions

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