RAID Calculator

Find usable storage capacity for a RAID array.

Number of disks

Disk size (TB)

RAID level

Usable capacity (TB) 12

Formula: Usable capacity depends on the RAID level

Step-by-step with your numbers:

1. Values used:

2. Number of disks = 4

3. Disk size = 4 TB

5. Usable capacity = 12TB

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RAID levels trade capacity for redundancy and speed.

The math behind it

RAID 0 = n x size, RAID 1 = size, RAID 5 = (n-1) x size, RAID 6 = (n-2) x size, RAID 10 = n/2 x size.

Four 4 TB disks in RAID 5 give 12 TB usable.

Which level is safest?

RAID 6 survives two disk failures; RAID 0 has no redundancy.