Raidcapacity Calculator
Our storage & raid tool computes raidcapacity accurately. Enter your inputs for detailed analysis and optimization tips.
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer
Raidcapacity Calculator
Calculator
Adjust values & calculateEnter your values below. Every result is computed in your browser — no data is sent to any server.
Formula: Usable = (N - P) x Disk Size
Worked example — Usable: 12,000 GB (12 TB) | Efficiency: 75% | Fault tolerance: 1 disk
Formula
Usable = (N - P) x Disk Size
Where N is the number of disks, P is the number of parity/mirror disks (varies by RAID level), and Disk Size is the capacity of each individual drive. RAID 0: P=0, RAID 1: P=N-1, RAID 5: P=1, RAID 6: P=2, RAID 10: P=N/2.
Worked Examples
Example 1: NAS with RAID 5
Problem:You have 4 x 4TB drives configured in RAID 5. Calculate usable capacity and storage efficiency.
Solution:Total raw capacity: 4 x 4,000 GB = 16,000 GB RAID 5 usable: (n-1) x disk size = 3 x 4,000 = 12,000 GB Parity overhead: 1 x 4,000 = 4,000 GB Storage efficiency: 12,000 / 16,000 = 75% Fault tolerance: 1 disk failure
Result:Usable: 12,000 GB (12 TB) | Efficiency: 75% | Fault tolerance: 1 disk
Example 2: Database Server with RAID 10
Problem:A database server uses 6 x 2TB SSDs in RAID 10. Calculate usable capacity and performance characteristics.
Solution:Total raw capacity: 6 x 2,000 GB = 12,000 GB RAID 10 usable: (n/2) x disk size = 3 x 2,000 = 6,000 GB Mirror overhead: 6,000 GB Storage efficiency: 6,000 / 12,000 = 50% Read performance: 6x single disk Write performance: 3x single disk
Result:Usable: 6,000 GB (6 TB) | Efficiency: 50% | Read: 6x, Write: 3x single disk speed
Frequently Asked Questions
What is RAID and why is it used in storage systems?
RAID stands for Redundant Array of Independent Disks. It is a technology that combines multiple physical hard drives or solid state drives into a single logical unit for improved performance, redundancy, or both. RAID was originally developed to make inexpensive disks work together to match the performance and reliability of more expensive drives. Different RAID levels offer different trade-offs between capacity, speed, and fault tolerance. RAID 0 maximizes speed with no redundancy, RAID 1 mirrors data for full redundancy, RAID 5 balances both with distributed parity, and RAID 6 adds an extra parity layer for double fault tolerance. RAID is fundamental in servers, NAS devices, and enterprise storage systems.
How does RAID 5 work and what happens when a disk fails?
RAID 5 distributes data and parity information across all member disks using a striping pattern. Parity is a calculated value that allows the array to reconstruct any single missing piece of data. When data is written, the RAID controller calculates parity using XOR operations and distributes it evenly across all disks. If one disk fails, the array enters a degraded state where it continues operating by computing the missing data on the fly from the remaining data and parity blocks. Performance drops significantly during degradation. A replacement disk triggers a rebuild process that can take hours to days depending on array size. During rebuild, the array is vulnerable because a second disk failure would cause total data loss.
What is the difference between RAID 5, RAID 6, and RAID 10?
RAID 5 uses single distributed parity, losing one disk worth of capacity and tolerating one disk failure. It requires minimum three disks and offers good read performance but slower writes due to parity calculations. RAID 6 uses double distributed parity, losing two disks worth of capacity and tolerating two simultaneous failures. It requires minimum four disks and is recommended for large arrays where rebuild times are long. RAID 10 combines mirroring and striping, losing half the total capacity but offering the best performance of all redundant RAID levels. It tolerates multiple failures as long as both disks in a mirror pair do not fail simultaneously. RAID 10 is preferred for database and high-performance workloads.
How do I calculate storage efficiency for different RAID levels?
Storage efficiency is the percentage of total raw disk capacity available for data storage. For RAID 0, efficiency is 100 percent since all capacity is usable with no redundancy overhead. For RAID 1 with two disks, efficiency is 50 percent because data is fully mirrored. For RAID 5, efficiency is (n-1)/n times 100, where n is the number of disks. With four disks, RAID 5 gives 75 percent efficiency. For RAID 6, efficiency is (n-2)/n times 100, giving 50 percent with four disks but 80 percent with ten disks. RAID 10 always gives 50 percent efficiency regardless of disk count. Larger arrays improve efficiency for parity-based RAID levels while mirroring efficiency remains constant.
Should I use hardware RAID or software RAID for my storage setup?
Hardware RAID uses a dedicated controller card with its own processor and cache memory to manage the array, offloading RAID calculations from the main CPU. It typically offers better performance, battery-backed cache for write protection during power loss, and is independent of the operating system. Software RAID uses the host operating system to manage the array through the CPU, offering lower cost and more flexibility. Modern software RAID implementations like Linux mdadm or ZFS provide excellent performance since modern CPUs easily handle parity calculations. For critical enterprise environments, hardware RAID with battery-backed cache is still preferred. For home servers and small businesses, software RAID provides comparable reliability at much lower cost.
References
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer · Editorial policy
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