RAID 5 Usable Capacity Calculator

To calculate the usable capacity of a RAID 5 array, you need to consider the following factors:

1. Number of Drives (N): This is the total number of drives in the RAID 5 array, including the parity drive.
2. Drive Capacity (D): The capacity of each individual drive in the RAID array, typically measured in terabytes (TB) or gigabytes (GB).
3. Total Capacity (TC): This is the total raw capacity of the RAID array before accounting for redundancy. It’s calculated by multiplying the number of drives by the capacity of each drive.
4. Parity Space: In RAID 5, one drive’s worth of capacity is reserved for parity data. This parity data is distributed across all drives in the array and is used for fault tolerance.
5. Usable Capacity (UC): This is the total amount of storage space available for data storage after accounting for redundancy.

Here’s a table to illustrate the calculation:

Factor	Calculation
Total Capacity (TC)	N * D
Parity Space	D
Usable Capacity (UC)	(N – 1) * D

Let’s assume you have a RAID 5 array with 5 drives, each with a capacity of 4TB:

1. Number of Drives (N): 5
2. Drive Capacity (D): 4TB

Now let’s calculate:

• Total Capacity (TC) = 5 * 4TB = 20TB
• Parity Space = 1 * 4TB = 4TB
• Usable Capacity (UC) = (5 – 1) * 4TB = 16TB

So, in this example, the usable capacity of the RAID 5 array would be 16TB.