RAID Toolkit

RAID Calculator

Work out the usable capacity, read speed gain, write penalty and fault tolerance of a RAID array. Choose a level, enter your disk count and single disk size, and the numbers update as you type.

Step 1

Input

Total disks in the array, hot spares included.

Bare numbers mean TB. You can also type 500gb, 7.68tb or 1tib.

Not sure which to pick? The types reference explains the trade-offs.

Step 2

Results

Waiting for valid input

Fill in the fields on the left to see your array’s numbers.

At a glance

Every level this calculator supports

Figures assume identical disks and exclude filesystem and controller overhead. Read the full reference for how each level works.

Per-disk-equivalent behaviour for an equal number of identical disks. “Space used” is the share of raw capacity consumed by parity, mirrors or spares.
Level Min disks Usable Space used Read gain Write penalty Can lose
RAID 0 2100%none N××10 disks
RAID 1 250%mirroring ×1×21 disk
RAID 1E 350%mirroring ×1×21 disk
RAID 5 3N−1 / Nparity N−1××41 disk
RAID 50 6~80%1 disk per group K×(G−1)×41 disk
RAID 5E / 5EE 4N−2 / Nparity + spare N−2××41 disk
RAID 10 450%mirroring N××21 disk per pair
RAID 6 4N−2 / Ndouble parity N−2××62 disks
RAID 60 850%2 disks per group K×(G−2)×62 disks

RAID is not a backup. It protects against a disk failing. It does nothing about deletion, corruption, ransomware, fire, theft or a controller that loses its metadata. Rebuilds also read every remaining disk, so an unrecoverable sector on a surviving drive can destroy a mirrored or parity-protected array. Keep a real, tested, off-site backup.