RAID Capacity Calculator
The RAID Capacity Calculator computes usable capacity (TB/TiB), storage efficiency, and fault tolerance for RAID 0, 1, 5, 6, 10, 50, 60, and JBOD configurations. Features include hot spare support, a side-by-side comparison table of all RAID levels, and a visual capacity breakdown bar.
Calculate usable capacity, redundancy, and efficiency of RAID arrays from drive count, capacity, and RAID level. Supports all RAID levels comparison and TB/TiB conversion.
Calculation Input
How to Use
Using the RAID Capacity Calculator is straightforward. Follow these steps:
- Enter the number of drives and the capacity per drive (GB/TB)
- Select the RAID level (for RAID 50/60, also set the sub-group count)
- Optionally enter the number of hot spares, then click the Calculate button
Check 'Also show real capacity (TiB)' to see the actual capacity recognized by the OS (binary-based).
What is RAID?
RAID (Redundant Array of Independent Disks) is a technology that combines multiple hard drives or SSDs to improve data redundancy (fault tolerance) and/or performance. It is widely used in servers, NAS devices, and data centers.
Different RAID levels offer different trade-offs between redundancy, usable capacity, and performance. Choosing the right level depends on your priorities — speed, safety, or a balance of both.
- RAID 0 (Striping): Distributes data across drives. Uses full capacity but offers no redundancy.
- RAID 1 (Mirroring): Copies data to all drives. Maximum redundancy but low capacity efficiency.
- RAID 5 (Single Parity): Distributes one drive's worth of parity data. Good balance of capacity and redundancy.
- RAID 6 (Double Parity): Two drives' worth of parity, tolerating 2 simultaneous failures. Ideal for large arrays.
- RAID 10 (1+0): Mirroring + striping. Combines high redundancy with high performance.
- RAID 50 (5+0): Striped RAID 5 groups. Improves performance and redundancy for large-scale deployments.
- RAID 60 (6+0): Striped RAID 6 groups. Maximum redundancy for large-scale environments.
- JBOD (Just a Bunch of Disks): Simply concatenates drives. No redundancy, full capacity available.
How to Choose the Right RAID Level
The best RAID level depends on your priorities and use case. Here we explain the optimal choice from three perspectives.
RAID Comparison Chart
| RAID Level | Min Drives | Usable Capacity | Read Speed | Write Speed | Fault Tolerance | ||
|---|---|---|---|---|---|---|---|
| Seq | Ran | Seq | Ran | ||||
JBOD Just a Bunch of Disks | 1 | N × D | ▰▱▱▱▱ | ▰▱▱▱▱ | ▰▱▱▱▱ | ▰▱▱▱▱ | × (None) |
RAID 0 Striping | 2 | N × D | ▰▰▰▰▰ | ▰▰▰▰▰ | ▰▰▰▰▰ | ▰▰▰▰▰ | × (None) |
RAID 1 Mirroring | 2 | 1 × D | ▰▰▱▱▱ | ▰▰▱▱▱ | ▰▰▱▱▱ | ▰▱▱▱▱ | 1 drive(s) |
RAID 5 Parity | 3 | (N−1) × D | ▰▰▰▰▱ | ▰▰▰▱▱ | ▰▰▰▱▱ | ▰▰▱▱▱ | 1 drive(s) |
RAID 6 Dual Parity | 4 | (N−2) × D | ▰▰▰▱▱ | ▰▰▱▱▱ | ▰▰▱▱▱ | ▰▰▱▱▱ | 2 drive(s) |
RAID 10 RAID 1+0 | 4 | N/2 × D | ▰▰▰▰▱ | ▰▰▰▰▱ | ▰▰▰▰▱ | ▰▰▰▰▱ | 1〜N/2 drive(s) |
RAID 50 RAID 5+0 | 6 | (N−G) × D | ▰▰▰▰▱ | ▰▰▰▱▱ | ▰▰▰▱▱ | ▰▰▰▱▱ | 1 per group |
RAID 60 RAID 6+0 | 8 | (N−2G) × D | ▰▰▰▱▱ | ▰▰▰▱▱ | ▰▰▰▱▱ | ▰▰▱▱▱ | 2 per group |
N = number of drives, D = capacity per drive, G = number of sub-groups
More ▰ = better performance (5-level scale)
Seq = Sequential access: throughput for large contiguous reads/writes
Ran = Random access: speed for small random I/O operations
When Performance Is the Priority
To maximize read/write speed, RAID 0 distributes data across all drives for the highest throughput, but offers no redundancy. If you need both speed and data protection, RAID 10 is the best choice — it combines mirroring for safety with striping for performance.
RAID 10 excels in database servers and virtualization environments with heavy random I/O. For primarily sequential read workloads, RAID 5 or RAID 6 can also deliver sufficient throughput.
When Data Protection Is the Priority
For mission-critical data, RAID 6 is recommended as it can survive two simultaneous drive failures. With large drives (4 TB+), rebuilds can take hours to days, and the risk of a second failure during that window is significant.
For even higher reliability in large-scale environments, consider RAID 60. It stripes RAID 6 sub-groups, tolerating two failures per sub-group. In all cases, provisioning one or two hot spares with automatic rebuild is essential.
When Cost Efficiency Is the Priority
To maximize storage capacity on a limited budget, RAID 5 offers the best balance. With only one drive's worth of parity overhead, capacity efficiency improves as you add more drives.
For file servers and NAS (home or small business), a 4–8 drive RAID 5 array is highly cost-effective. However, for larger arrays (8+ drives), consider moving to RAID 6 for added safety during rebuilds.
Real-World RAID Configuration Examples
The ideal RAID level varies by use case. Below are typical configurations and their recommended RAID setups.
| Use Case | Configuration | RAID Level | Usable Capacity | Notes |
|---|---|---|---|---|
| Home NAS | 4 × 4 TB | RAID 5 | 12 TB | Ideal for photo/video storage. Tolerates 1 failure |
| SMB File Server | 8 × 8 TB | RAID 6 | 48 TB | Business data protection. Tolerates 2 failures |
| Database Server | 6 × 1 TB | RAID 10 | 3 TB | High-speed I/O with redundancy |
| Enterprise Storage | 24 × 16 TB + 1 spare | RAID 6 | 352 TB | Maximum redundancy with hot spare |
These are typical configurations. Enter your actual drive capacity and count in the calculator above to compute the exact usable capacity.
Frequently Asked Questions
- What is the difference between TB and TiB?
- TB (terabyte) is decimal (1 TB = 1,000 GB = 10^12 bytes), while TiB (tebibyte) is binary (1 TiB = 1,024 GiB = 2^40 bytes). Drive manufacturers label drives in TB, but operating systems display capacity in TiB, so a 1 TB drive shows as approximately 931 GiB in your OS.
- What is a hot spare?
- A hot spare is a standby drive in a RAID array. When a drive fails, the hot spare automatically takes over and the array begins rebuilding data onto it. It does not contribute to usable capacity but significantly reduces recovery time.
- Should I choose RAID 5 or RAID 6?
- RAID 5 tolerates one drive failure, but with large drives, a second failure during rebuild is a real risk. For drives of 4 TB or more, or when using many drives, RAID 6 is recommended because it can survive two simultaneous failures.
- How should I choose the sub-group count for RAID 50/60?
- The sub-group count must be 2 or more and must evenly divide the total drives (excluding hot spares). More sub-groups improve performance but reduce capacity efficiency. A common recommendation is 4–8 drives per sub-group.
- Can RAID replace backups?
- No, RAID is not a substitute for backups. RAID maintains data availability during drive failures, but it cannot protect against accidental file deletion, ransomware, controller failure, or disasters. It is essential to maintain regular backups (following the 3-2-1 rule) alongside RAID.
- Is RAID effective with SSDs?
- Yes, RAID is effective with SSDs. While SSDs have lower failure rates than HDDs, drives from the same batch tend to reach end-of-life around the same time, making RAID 6 or RAID 10 recommended for redundancy. Also note that SSD RAID performance may be bottlenecked by the controller or interface rather than the drives themselves.
- What is the purpose of RAID 0 if it has no fault tolerance?
- RAID 0's primary value is speed through striping. Data is distributed across multiple drives for parallel read/write, scaling throughput roughly with the number of drives. It also uses 100% of total drive capacity. It is suited for workloads where data can be recovered from other sources — video editing scratch space, cache servers, or temporary computation data.
- What is the difference between RAID 0 and JBOD?
- Both combine multiple disks into a single volume, but the mechanism differs. JBOD simply concatenates disks end-to-end with no speed benefit. RAID 0 stripes data across all drives, improving read/write speed proportionally to the number of drives. Use JBOD when you only need to merge capacity; use RAID 0 when you also need speed.
IP Subnet Calculator
When building servers with RAID, network design is equally important. The IP Subnet Calculator computes network address, broadcast, and available host count from an IP address and subnet mask.