RAID Calculator

How to use

To use the calculator, enter your application’s total IOPS, maximum of 999,999.
Example: 500
Then enter the percentage that are read IOPS, 0-100.
Example: 25
Select your disk size.
Example: 300GB 15K
Click Submit.


Disk IOPS used in the calculator are average IOPS per disk type.
SSD = ~5250 IOPS
15K = ~175 IOPS
10K = ~135 IOPS
7.2K = ~75 IOPS

  • sirenozap

    This is wrong. RAID 0 will get better performance than RAID 5 and RAID 5 will get better performance than RAID6.

    • Paul Richards

      You are correct – R0 is better performing than R5, R5 is better performing than R6. However, that’s not what I’m saying with this post. The point of this calculator is to illustrate the importance of choosing the proper RAID type for your workload. For example: If you want to hit a certain performance threshold, you would require more disks for RAID5 than you would for RAID0, and more for RAID6 than for RAID5. That’s what the calculations show. Granted the calculator is not very realistic in some scenarios because things like caching, wide striping, and maximum disks per RAID type are not factored into the calculations. But eventually when I have some free time, I’ll make that happen. Thanks for your comment.

    • Cody

      Paul is right.. you aren’t looking at how many spindles are being shown for each RAID group. For example, an app requiring 3,000 IOPS can get this from 23 drives (900 GB 10K) using RAID-0, or from 36 drives (900 GB 10K) using RAID-5. Not many people actually understand RAID. I have to keep explaining this to people myself. Yes, RAID-0 performs better than RAID-5, but that doesn’t mean you can’t make RAID-5 out perform RAID-0 with enough spindles. A RAID-5 array with 30 disks is always going to out perform a RAID-0 array with 12 disks. I had a developer request a single pair of drives (2 drives total) because he thought RAID-1 would be better than RAID-5 for his database logs. That’s not true, the RAID type alone doesn’t determine performance. Also, not all SANs have the same max drive limit per RAID group either. Compellent arrays are a prime example of this.

  • Wmarow

    habe you tried my array estimator? – it does similar job.

    • Paul Richards

      Awesome! I bookmarked your site for future ref :)

      Thanks for checking out my calc.

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