Best RAID Level for 2, 3, 4, 5, 6 or 8 Drives
The drive count limits which RAID levels you can build. Within those, the choice is a trade between usable space, how many failures the array survives, and write speed.
Quick picks
- 2 drives: RAID 1 (mirror).
- 3 drives: RAID 5.
- 4 drives: RAID 10 for write speed, or RAID 6 to survive any two failures; both leave two drives of space.
- 5 or more drives: RAID 6 for large drives; RAID 10 with an even count when random-write speed matters most.
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.
Options by drive count
| Drives | Levels that work: usable space and failures survived |
|---|---|
| 2 | RAID 0: 2 drives of space, survives none · RAID 1: 1 drive of space, survives 1 |
| 3 | RAID 0: 3 drives of space, survives none · RAID 5: 2 drives of space, survives 1 |
| 4 | RAID 0: 4 drives of space, survives none · RAID 5: 3 drives of space, survives 1 · RAID 6: 2 drives of space, survives 2 · RAID 10: 2 drives of space, survives 1–2 |
| 5 | RAID 0: 5 drives of space, survives none · RAID 5: 4 drives of space, survives 1 · RAID 6: 3 drives of space, survives 2 |
| 6 | RAID 0: 6 drives of space, survives none · RAID 5: 5 drives of space, survives 1 · RAID 6: 4 drives of space, survives 2 · RAID 10: 3 drives of space, survives 1–3 |
| 8 | RAID 0: 8 drives of space, survives none · RAID 5: 7 drives of space, survives 1 · RAID 6: 6 drives of space, survives 2 · RAID 10: 4 drives of space, survives 1–4 |
Space is in drives of capacity; multiply by your drive size. RAID 10 needs an even count; RAID 0 survives no failures.
Two or three drives
With two drives the choice is RAID 1 (one drive of space, survives one failure) or RAID 0 (no protection). Three drives allow RAID 5: two drives of space and one failure.
Four drives
RAID 6 and RAID 10 both leave two drives of space. RAID 6 survives any two failures; RAID 10 writes faster but loses data if both drives of one pair fail. RAID 5 gives three drives of space with one drive of protection.
Five drives and more
As the count grows, RAID 6 keeps more of the raw space (all but two drives) while surviving any two failures, which suits large nearline drives. RAID 10 keeps half the space and suits databases and virtual machines.
16TB drives for this array
In-stock 16TB drives from our catalogue, with the price for the 6 drives in the example above. Hot spares are extra.
- SHD7B06079 - Lenovo 16TB SATA 3.5-Inch Hot-Swap Hard Drive (512e, SED) $247.50 each · 6 drives $1,485.00
- Seagate ST16000NM010G Exos X16 16TB 7200RPM 12Gb/s SAS 256MB Cache 512e Enterprise $429.47 each · 6 drives $2,576.82
- ST16000NM003G - Seagate Exos X16 16TB 7200RPM SATA 6Gb/s 256MB Cache 512e Sed 3.5-inch $447.37 each · 6 drives $2,684.22
- ST16000NM002G - Seagate Exos X16 16TB 7200RPM SAS 12Gb/s 256MB Cache 512e 3.5-inch Hard $450.53 each · 6 drives $2,703.18
- ST16000VN001 - Seagate IronWolf Nas 16TB 7200RPM SATA 6Gb/s 256MB Cache 3.5-inch Hard $468.42 each · 6 drives $2,810.52
- Seagate ST16000NM007H Exos X24 16TB 7200RPM 12Gb/s SAS 512MB Cache 512e 3.5-Inch Hard $478.95 each · 6 drives $2,873.70
- Toshiba MG08ACA16TE 16TB 7200RPM 6Gb/s SATA 512MB Cache 512e 3.5-Inch Hard Drive $468.42 each · 6 drives $2,810.52
- Seagate ST16000NM004G Exos X16 16TB 7200RPM 12Gb/s SAS 256MB Cache Self-Encrypting Drives $500.00 each · 6 drives $3,000.00
Frequently asked questions
What is the best RAID for 4 drives?
RAID 6 or RAID 10, which both leave two drives of usable space. RAID 6 survives any two failures; RAID 10 has faster random writes.
Can RAID 6 use only 4 drives?
Yes. Four is the minimum for RAID 6, giving two drives of usable space.
What RAID level should I use for a home NAS?
With large drives, RAID 6 (or your NAS vendor’s two-drive-protection mode) keeps protection during a rebuild. RAID 5 gives more space with one drive of protection. Either way, keep a separate backup.
RAID calculators by level
- RAID calculator (all levels)
- RAID 0 calculator
- RAID 1 calculator
- RAID 5 calculator
- RAID 6 calculator
- RAID 10 calculator
- RAID 50 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
- RAID 50 vs RAID 60
- RAID 6 vs RAID 60
Related
Updated 2026-10-22.