Limit Table Calculator

If you’re managing a RAID 5 storage setup or planning to build one, understanding how much usable storage you’ll have is critical. Our RAID 5 Capacity Calculator is a powerful, free-to-use tool that helps you quickly determine your usable capacity and parity overhead based on the total number of disks and their size.

RAID 5 is one of the most popular RAID levels due to its balance of performance, fault tolerance, and efficient disk usage. However, calculating storage efficiency can be confusing, especially for newcomers. This easy-to-use calculator solves that problem by automating the math for you.

🔧 How to Use the RAID 5 Capacity Calculator

Using the calculator is simple and only takes a few seconds:

  1. Enter the Total Number of Disks
    Input the total number of physical hard drives (or SSDs) in your RAID 5 setup. RAID 5 requires at least 3 disks.
  2. Enter the Disk Size (GB)
    Input the capacity of each disk in gigabytes (GB). All disks must be of the same size in a RAID 5 array for this calculator to work correctly.
  3. Click “Calculate”
    The tool instantly computes:
    • Usable Capacity: Total storage available after accounting for parity.
    • Parity Overhead: Space used for fault-tolerant parity data.
  4. Click “Reset” if you want to clear the fields and start over.

The results appear just below the form, clearly labeled and easy to understand.

💡 Example: RAID 5 Capacity Calculation

Let’s say you’re setting up a RAID 5 array with 5 disks, each 2,000 GB (2 TB) in size.

Step-by-step Calculation:

  • Total Disks: 5
  • Disk Size: 2000 GB
  • Usable Capacity: (5 – 1) × 2000 = 8,000 GB
  • Parity Overhead: 2000 GB

So, in this setup, you’ll have 8 TB of usable storage, and 2 TB will be reserved for parity data. This configuration allows one disk to fail without data loss.

📘 Understanding RAID 5

What is RAID 5?

RAID 5 (Redundant Array of Independent Disks) uses block-level striping with distributed parity. It offers a smart blend of performance, redundancy, and storage efficiency. Here’s how it works:

  • Data is striped across all disks.
  • Parity data is distributed evenly among all drives.
  • You only lose the capacity of one disk for parity, no matter how many total disks you have.
  • Minimum of 3 disks required.
  • Can survive the failure of 1 disk.

🔍 Why Use This RAID 5 Calculator?

  • ✅ Quick and accurate parity and storage calculation
  • ✅ Helps with storage planning and hardware purchasing decisions
  • ✅ Great for home labs, SMBs, and enterprise IT
  • ✅ Free to use and accessible online
  • ✅ No registration or downloads required

🧠 Additional Tips for RAID 5 Planning

  • Use identical disks: All disks should be the same size for maximum efficiency.
  • Watch for rebuild time: While RAID 5 can survive a single disk failure, rebuilding can be slow and stressful on remaining drives.
  • Backup anyway: RAID is not a backup solution. Always back up your data.
  • SSD or HDD? RAID 5 works with both, but SSDs have faster performance and rebuild times.
  • Consider RAID 6 if you need to tolerate two disk failures.

❓ Frequently Asked Questions (FAQs)

1. What is RAID 5?

RAID 5 is a fault-tolerant storage configuration using striping with distributed parity. It allows one disk failure without data loss.

2. How many disks do I need for RAID 5?

A minimum of 3 disks is required to set up RAID 5.

3. What is “usable capacity” in RAID 5?

Usable capacity is the total storage available after subtracting the space used for parity. It’s calculated as (total disks - 1) × disk size.

4. What is “parity overhead”?

Parity overhead is the storage space used to store parity data, which enables data recovery if a disk fails.

5. Can I mix disk sizes in RAID 5?

Technically yes, but it’s not recommended. RAID 5 uses the smallest disk size across all disks, which can waste space.

6. Is RAID 5 suitable for SSDs?

Yes, RAID 5 works with SSDs. In fact, SSDs can improve rebuild times and performance.

7. What happens if two disks fail in RAID 5?

RAID 5 can only tolerate one disk failure. If a second disk fails before the first is rebuilt, data loss occurs.

8. How do I rebuild a failed RAID 5 array?

After replacing the failed disk, the RAID controller or software will automatically rebuild the array using parity data. This can take hours.

9. Is RAID 5 good for gaming or media storage?

RAID 5 is excellent for media servers and gaming libraries that need large, fault-tolerant storage.

10. What are alternatives to RAID 5?

  • RAID 6 (tolerates 2 failures)
  • RAID 10 (high performance + redundancy)
  • RAID 1 (mirroring)
  • JBOD (no redundancy)

11. Can I expand a RAID 5 array later?

Yes, but it depends on your RAID controller or software. Not all support online capacity expansion.

12. Does RAID 5 improve performance?

It can improve read performance, but write speeds are generally slower than RAID 0 due to parity calculations.

13. Should I use hardware or software RAID?

Hardware RAID offers better performance and features, while software RAID is more flexible and cost-effective.

14. What if my RAID 5 array crashes?

Professional data recovery services may be able to help. Always maintain external backups.

15. How do I calculate RAID 5 storage manually?

Use the formula: (Number of Disks - 1) × Size of Smallest Disk.

16. Is RAID 5 safe for critical data?

It’s reasonably safe but not a substitute for backups. Always use a 3-2-1 backup strategy.

17. Does RAID 5 reduce overall disk lifespan?

Not inherently, but rebuild operations can stress healthy disks, especially during a failure.

18. Can I use RAID 5 for video editing?

Yes, but RAID 10 or SSD-based RAID 5 is preferred for higher performance.

19. What file systems are compatible with RAID 5?

NTFS, ext4, XFS, and others — compatibility depends on your OS and RAID setup.

20. How long does it take to rebuild a RAID 5 array?

Rebuild time depends on disk size and system speed, but can range from several hours to over a day for large arrays.

🎯 Final Thoughts

The RAID 5 Capacity Calculator is an essential utility for anyone working with RAID-based storage systems. Whether you’re an IT professional, a system builder, or a tech-savvy home user, this tool helps ensure you’re making the most of your disk array—without sacrificing reliability.

Use it now to plan smarter, save time, and prevent storage surprises down the road.