RAID Calculator

Redundant Array of Independent Disks (RAID) configurations combine multiple physical hard drives into a single logical unit to improve performance, provide redundancy, or both. Each RAID level uses a specific mathematical formula to balance capacity and safety. For instance, in a RAID 0 setup, usable capacity is simply the sum of all disks: Capacity = N × Disk Size, offering zero fault tolerance but maximum speed. Conversely, RAID 5 dedicates the equivalent of one disk's space to distributed parity, yielding a usable capacity of (N - 1) × Disk Size while allowing the array to survive a single drive failure. Advanced nested levels like RAID 10 combine mirroring and striping, requiring a minimum of four drives and offering a usable capacity of half the total raw storage.

Let's evaluate a standard enterprise storage scenario using 4 hard drives, each with a capacity of 2 Terabytes (TB), priced at $150 per disk, configured in a RAID 5 array. First, calculate the total raw disk space: 4 drives × 2 TB = 8 TB raw capacity. For RAID 5, the usable storage formula is (N - 1) × Disk Size, which translates to (4 - 1) × 2 TB = 6 TB of usable capacity. The remaining 2 TB is utilized for distributed parity, granting a fault tolerance of 1 failed drive. The total hardware cost is 4 disks × $150 = $600. Dividing the total cost by the usable capacity ($600 / 6 TB) gives a highly efficient cost of $100 per usable TB.

When designing your storage array, keep these crucial guidelines in mind to protect your data and maximize performance:
1. RAID is not a backup: Redundancy protects against hardware failure and keeps your system online, but it does not protect against accidental deletion, ransomware, or file corruption. Always maintain offsite backups.
2. Match drive specifications: For optimal performance and longevity, use drives of the exact same capacity, speed, and ideally the same manufacturer batch.
3. Factor in rebuild times: Larger capacity drives take significantly longer to rebuild after a failure, increasing the vulnerability window during a degraded state.