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RAID Calculator
Compare RAID 0, 1, 5, 6, 10 and more: usable capacity, fault tolerance, read/write performance and rebuild time for your disks.
Configuration
Results, RAID 5
min 3 disksUsable capacity
11.4 TB
Raw capacity
16.0 TB
Lost to redundancy
4.00 TB
Fault tolerance
1 disk
Efficiency
75%
Rebuild / disk
10.6 h
Read speed
3× disk
Write speed
3× disk
Striping with distributed single parity. Survives one disk failure. Watch rebuild times on large drives.
Compare all RAID levels
For 4 × 4 TB disks
| Level | Usable | Fault tolerance | Efficiency | Min disks |
|---|---|---|---|---|
| JBOD | 15.2 TB | 0 disks | 100% | 1 |
| RAID 0 | 15.2 TB | 0 disks | 100% | 2 |
| RAID 1 | 3.80 TB | 3 disks | 25% | 2 |
| RAID 5 | 11.4 TB | 1 disk | 75% | 3 |
| RAID 6 | 7.60 TB | 2 disks | 50% | 4 |
| RAID 10 | 7.60 TB | 2 disks | 50% | 4 |
| RAID 50 | - | n/a | - | 6 |
| RAID 60 | - | n/a | - | 8 |
RAID quick reference
JBOD
NoneDisks are concatenated into one volume. No striping, no redundancy — a single disk failure loses that disk's data.
Concatenated storage, scratch data
RAID 0
NoneData is striped across all disks for maximum performance and full capacity, but any single disk failure destroys the whole array.
Max speed & capacity, no protection
RAID 1
n − 1 disksEvery disk is an exact mirror. Survives loss of all but one disk, but usable capacity equals a single disk.
OS / boot drives, critical small volumes
RAID 5
1 diskStriping with distributed single parity. Survives one disk failure. Watch rebuild times on large drives.
General-purpose, good capacity + protection
RAID 6
2 disksStriping with double parity. Survives two simultaneous disk failures — preferred for large-capacity drives.
Large arrays, safer rebuilds
RAID 10
1 per mirror (up to n/2)Mirrored pairs that are then striped. Great performance and fast rebuilds; usable capacity is half the raw.
Databases, high IOPS workloads
RAID 50
1 per groupMultiple RAID 5 groups striped together. Tolerates one failure per group with better performance than a single RAID 5.
Large, fast, capacity-oriented arrays
RAID 60
2 per groupMultiple RAID 6 groups striped together. Tolerates two failures per group — strong protection at scale.
Very large arrays needing resilience
About this tool
The RAID calculator shows usable capacity, redundancy and the read/write trade-offs for common RAID levels (0, 1, 5, 6, 10 and more) based on your disk count and drive size. It is the fastest way to answer "how much space do I actually get, and how many disks can fail?" before buying hardware.
Use it to compare layouts side by side: a RAID 6 array sacrifices two disks of capacity for two-drive fault tolerance, while RAID 10 trades half your raw capacity for the best rebuild and write performance. Everything is computed in the browser.
Frequently asked questions
How much capacity do I lose with RAID 5 vs RAID 6?+
RAID 5 uses the equivalent of one disk for parity, RAID 6 uses two. With eight 4 TB disks you get roughly 28 TB usable on RAID 5 and 24 TB on RAID 6, in exchange for surviving two simultaneous failures.
Is RAID a backup?+
No. RAID protects against disk failure, not against deletion, ransomware or controller faults. Always keep separate, ideally offsite, backups in addition to any RAID level.
Which RAID level is best for write-heavy workloads?+
RAID 10 generally offers the best write performance and fastest rebuilds, at the cost of 50% usable capacity. RAID 5/6 are more space-efficient but carry a write penalty from parity calculations.