RAID Capacity Calculator
Estimate equal-disk RAID capacity, disk-failure tolerance and a full-disk rebuild time from your supplied rate.
A QUICK WALKTHROUGH
How to use this tool
- Enter the values and choose their units.
- Use 2–128 equal-size disks (RAID 0 also allows 1), >0 to 1,000 TB or TiB per disk, reserve 0–99%, and a supplied rebuild rate >0 to 1,000,000 MB/s. RAID 0: N×C, 0 failures; RAID 1: C, N−1 failures; RAID 5: (N−1)×C, 1 failure, N≥3; RAID 6: (N−2)×C, 2 failures, N≥4; RAID 10: N×C/2, even N≥4. RAID 10 guarantees any one failure; up to N/2 only if different mirror pairs fail. Reserve is removed after RAID overhead. Rebuild hours=one full disk in bytes/rate in decimal MB/s/3,600, ignoring workload, overhead and read errors. TB=10¹² bytes; TiB=2⁴⁰ bytes. Rebuild time is shown as — for RAID 0 or an omitted rate. No hardware performance or data-safety guarantee.
- Review the calculated result.
Formula and assumptions
Use 2–128 equal-size disks (RAID 0 also allows 1), >0 to 1,000 TB or TiB per disk, reserve 0–99%, and a supplied rebuild rate >0 to 1,000,000 MB/s. RAID 0: N×C, 0 failures; RAID 1: C, N−1 failures; RAID 5: (N−1)×C, 1 failure, N≥3; RAID 6: (N−2)×C, 2 failures, N≥4; RAID 10: N×C/2, even N≥4. RAID 10 guarantees any one failure; up to N/2 only if different mirror pairs fail. Reserve is removed after RAID overhead. Rebuild hours=one full disk in bytes/rate in decimal MB/s/3,600, ignoring workload, overhead and read errors. TB=10¹² bytes; TiB=2⁴⁰ bytes. Rebuild time is shown as — for RAID 0 or an omitted rate. No hardware performance or data-safety guarantee.
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Inputs stay in this browser; nothing is sent.
GOOD TO KNOW
Common questions
How is the result calculated?
Use 2–128 equal-size disks (RAID 0 also allows 1), >0 to 1,000 TB or TiB per disk, reserve 0–99%, and a supplied rebuild rate >0 to 1,000,000 MB/s. RAID 0: N×C, 0 failures; RAID 1: C, N−1 failures; RAID 5: (N−1)×C, 1 failure, N≥3; RAID 6: (N−2)×C, 2 failures, N≥4; RAID 10: N×C/2, even N≥4. RAID 10 guarantees any one failure; up to N/2 only if different mirror pairs fail. Reserve is removed after RAID overhead. Rebuild hours=one full disk in bytes/rate in decimal MB/s/3,600, ignoring workload, overhead and read errors. TB=10¹² bytes; TiB=2⁴⁰ bytes. Rebuild time is shown as — for RAID 0 or an omitted rate. No hardware performance or data-safety guarantee.