# RAID Calculator

Calculate RAID array capacity, storage efficiency, and fault tolerance for RAID 0, 1, 5, 6, and 10. Enter disk count and size to plan your storage.

## What this calculates

Planning a disk array? Enter your RAID level, number of disks, and disk size to see usable capacity, storage efficiency, and fault tolerance at a glance. Covers RAID 0, 1, 5, 6, and 10.

## Inputs

- **RAID Level** — options: RAID 0 (Striping), RAID 1 (Mirroring), RAID 5 (Striping + Parity), RAID 6 (Striping + Double Parity), RAID 10 (Mirrored Stripes) — Select the RAID configuration type
- **Number of Disks** — min 2, max 64 — Total number of physical disks in the array
- **Disk Size** — min 0.1
- **Size Unit** — options: GB, TB

## Outputs

- **Usable Capacity** — formatted as text — Total usable storage after RAID overhead
- **Raw Capacity** — formatted as text — Total raw storage before RAID
- **Storage Efficiency** — formatted as percentage
- **Fault Tolerance** — formatted as text — Number of drives that can fail without data loss
- **Minimum Disks Required**
- **Parity / Mirror Overhead** — formatted as text

## Details

RAID levels at a glance:

  - RAID 0 (Striping) -- splits data across all disks for speed. No redundancy. If one disk dies, everything is gone.

  - RAID 1 (Mirroring) -- duplicates data on every disk. Maximum safety, but you only get the capacity of one drive.

  - RAID 5 (Striping + Parity) -- distributes parity across all disks. Survives one disk failure. Needs at least 3 disks.

  - RAID 6 (Double Parity) -- like RAID 5 but survives two simultaneous disk failures. Needs at least 4 disks.

  - RAID 10 (Mirrored Stripes) -- combines RAID 1 mirrors into a RAID 0 stripe. Fast reads, survives one failure per mirror pair. Needs at least 4 disks (even number).

Choosing a RAID level:

  - Need pure speed with no safety net? RAID 0.

  - Need maximum reliability for critical data? RAID 1 or RAID 10.

  - Want a balance of capacity, speed, and safety? RAID 5 is the most popular choice.

  - Running a server where downtime is expensive? RAID 6 gives you room to lose two disks while you source replacements.

Remember: RAID is not a backup. It protects against hardware failure, not accidental deletion, ransomware, or controller failure. Always keep separate backups.

## Frequently Asked Questions

**Q: Which RAID level should I use for a home NAS?**

A: RAID 5 is the most popular choice for home NAS setups with 3-5 drives. It gives you a good balance of usable space and protection against a single drive failure. If you have 4+ drives and want extra safety, RAID 6 lets you survive two simultaneous failures.

**Q: Can I mix different size drives in a RAID array?**

A: Technically yes, but most RAID implementations will treat every drive as if it were the size of the smallest drive. So if you mix a 2 TB and a 4 TB drive, you effectively have two 2 TB drives. It is best to use identical drives.

**Q: Is RAID 10 better than RAID 5?**

A: RAID 10 offers faster write speeds and quicker rebuild times, but uses 50% of your raw capacity for redundancy. RAID 5 is more space-efficient (loses only one disk worth of capacity) but has slower writes and longer rebuild times on large arrays. For databases and write-heavy workloads, RAID 10 is often preferred.

**Q: Why is RAID not a backup?**

A: RAID protects against individual disk failure, but it cannot protect against accidental file deletion, ransomware, firmware bugs, or a failed RAID controller that corrupts all the disks at once. A real backup is a separate copy of your data stored on a different device or location.

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Source: https://vastcalc.com/calculators/everyday/raid
Category: Everyday Life
Last updated: 2026-04-08