RAID 50 Calculator
RAID 50 stripes data across two or more RAID 5 groups. Each group loses one drive to parity and can survive one failure of its own.
RAID 50 at a glance
- 12 × 10TB in RAID 50 = 100TB usable (90.95 TiB), 83% of raw capacity; survives at least 1 drive failure, up to 2 if each is in a different group.
- 100TB usable from 10TB drives in RAID 50 takes 12 drives (100TB usable).
Identical drives; decimal TB as drives are sold, binary TiB as most operating systems show it; before filesystem overhead. Hot spares are extra drives and add no capacity.
RAID 50 usable capacity by drive count
| Drives | 1.92TB | 3.84TB | 8TB | 12TB | 16TB | 24TB |
|---|---|---|---|---|---|---|
| 6 (2 groups) | 7.68TB | 15.36TB | 32TB | 48TB | 64TB | 96TB |
| 8 (2 groups) | 11.52TB | 23.04TB | 48TB | 72TB | 96TB | 144TB |
| 10 (2 groups) | 15.36TB | 30.72TB | 64TB | 96TB | 128TB | 192TB |
| 12 (2 groups) | 19.2TB | 38.4TB | 80TB | 120TB | 160TB | 240TB |
| 16 (2 groups) | 26.88TB | 53.76TB | 112TB | 168TB | 224TB | 336TB |
| 24 (2 groups) | 42.24TB | 84.48TB | 176TB | 264TB | 352TB | 528TB |
Usable capacity in decimal TB, before filesystem overhead. — means the drive count is not valid for RAID 50.
RAID 50 formula
Usable capacity = (n − g) × S, where g is the number of RAID 5 groups (at least 2, each with at least 3 drives and the same drive count). Minimum 6 drives. Example: 12 × 10TB in 2 groups = 100TB; in 3 groups = 90TB.
Fault tolerance
One drive per group is guaranteed: the array survives 1 failure anywhere, and up to g failures if each lands in a different group. Two failures in the same group lose the array.
More groups, less capacity
Each extra group costs one more drive of parity but shortens rebuilds and spreads risk. Dell PERC calls the group count "span depth"; HPE Smart Array calls it "parity groups".
10TB drives for this array
In-stock 10TB drives from our catalogue, with the price for the 12 drives in the example above. Hot spares are extra.
- P09149-B21 - HP 10TB 7200RPM SAS 12Gb/s Midline 3.5-inch Hard Drive $178.95 each · 12 drives $2,147.40
- 02YH266 - Lenovo WD 10TB 7.2K RPM SATA 3.5-Inch Hard Drive $225.00 each · 12 drives $2,700.00
- 05M0FD - Dell 10TB 7200RPM SAS12Gb/s 256MB Cache Hot-Pluggable 3.5-inch Hard Drive $254.40 each · 12 drives $3,052.80
- 0F27353 - HGST Ultrastar He10 10TB 7200RPM SAS 12Gb/s 512e Self-Encrypting 256MB Cache $240.00 each · 12 drives $2,880.00
- SHD7A74280 - Lenovo WD 10TB 7.2K RPM SATA 3.5-Inch Hard Drive $225.00 each · 12 drives $2,700.00
- 400-BEGN - Dell 10TB 7200RPM SAS12Gb/s 256MB Cache Hot-Pluggable 3.5-inch Hard Drive $334.74 each · 12 drives $4,016.88
- HUH721010AL5201 - Hitachi 10TB 7200RPM SAS 12Gb/s 3.5-inch Hard Drive $240.00 each · 12 drives $2,880.00
- MG06ACA10TE - Toshiba 10TB 7200RPM SATA 6Gb/s 3.5-inch Hard Drive $270.00 each · 12 drives $3,240.00
Frequently asked questions
What is the usable capacity of 12 × 10TB drives in RAID 50?
100TB with 2 groups of 6 (90.95 TiB), or 90TB with 3 groups of 4, before filesystem overhead.
What is the minimum number of drives for RAID 50?
Six: two RAID 5 groups of three drives each.
RAID 50 or RAID 6?
With the same drives, RAID 50 in 2 groups and RAID 6 give the same capacity, but RAID 6 survives any two failures, while RAID 50 loses data if both failures are in one group.
How many drives can fail in RAID 50?
At least one, and up to one per RAID 5 group, as long as no group loses two drives.
RAID calculators by level
- RAID calculator (all levels)
- RAID 0 calculator
- RAID 1 calculator
- RAID 5 calculator
- RAID 6 calculator
- RAID 10 calculator
- RAID 60 calculator
RAID planning guides
- How Many Drives Can Fail in Each RAID Level?
- RAID Hot Spare: What It Does and How It Affects Capacity
- TB vs TiB: Why a 24TB Drive Shows 21.8 TiB
- RAID Write Penalty by Level
- Best RAID Level for 2, 3, 4, 5, 6 or 8 Drives
- RAID 50 vs RAID 60
- RAID 6 vs RAID 60
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Updated 2026-10-22.