How To Calculate RAID 5 Capacity
One of the most popular RAID configurations is RAID 5, which combines performance, fault tolerance, and cost efficiency. In short, RAID 5 arrays distribute data across multiple drives while using parity information to recover lost data in the event of disk failures.
In this blog, we will learn how to calculate RAID 5’s storage capacity.
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RAID 5 Storage Capacity
In RAID 5, data and parity information are distributed across the array of disks. The parity information is essential for data reconstruction in the event of a drive failure. To calculate the storage capacity of a RAID 5 array, we need to consider several factors, such as the number of drives and their sizes.
RAID 5 Capacity Formula
The RAID 5 capacity can be calculated using the following formula:
C = (N — 1) * S
- N — Total number of all drives
- S — Size of the smallest drive
To understand the formula better, let’s break it down:
The “N — 1” term represents the number of data drives in the array, excluding the parity drive. Since RAID 5 requires at least three drives, we always have at least two data drives.
The “S” variable is the size of the smallest disk within the RAID 5 array. As all drives in the array must have the same size, using the smallest disk size (S) ensures uniformity. RAID controllers divide hard disk space into arrays based on the smallest drive in the array. For example, in a RAID 5 configuration with three drives of 500 GB, 200 GB, and 100 GB, each drive has a maximum of 100 GB assigned to the array.
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RAID 5 Capacity Calculation Example
To illustrate the RAID 5 capacity calculation, let’s consider a practical example.
Suppose we have a RAID 5 array with 5 drives (5 TB, 4 TB, 3 TB, 1 TB, and 10 TB). The total number of drives is 5, so N = 5. The smallest drive is 1 TB; therefore, S = 1. With these variables and the formula provided in the previous section, we will get the following result:
C = (5–1) * 1 TB = 4 * 1 TB = 4 TB
In this example, the total storage capacity of the RAID 5 array would be 4 terabytes.
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