RAID capacity and purchase-cost calculator
Seagate IronWolf RAID Calculator: Usable Capacity and Cost
Compare raw capacity, simplified usable capacity, operating-system-visible TiB, reserve-adjusted working space and drive cost for an IronWolf array. The calculator validates minimum drive counts and warns where RAID is being mistaken for backup.
Quick answer
RAID usable capacity depends on both drive size and layout. RAID 1 normally provides one drive’s capacity, RAID 5 uses the equivalent of one drive for parity, RAID 6 uses two, and RAID 10 provides half the raw capacity. Actual usable space is lower after binary reporting, metadata, file-system overhead, snapshots and reserved free space.
Exact model data
Exact IronWolf models available in the calculator
| Capacity | Family | Model | RPM | Recording | Cache | Max sustained | Workload | Warranty | Best fit |
|---|---|---|---|---|---|---|---|---|---|
| 2TB | IronWolf | ST2000VN003 | 5,400 | CMR | 256MB | 180MB/s | 180TB/year | 3 years | Compact home NAS and light backup |
| 4TB | IronWolf | ST4000VN006 | 5,400 | CMR | 256MB | 202MB/s | 180TB/year | 3 years | Two-bay backup and starter media NAS |
| 6TB | IronWolf | ST6000VN006 | 5,400 | CMR | 256MB | 202MB/s | 180TB/year | 3 years | Balanced home NAS capacity |
| 8TB | IronWolf | ST8000VN002 | 5,400 | CMR | 256MB | 202MB/s | 180TB/year | 3 years | Lower-power 8TB arrays |
| 8TB | IronWolf | ST8000VN004 | 7,200 | CMR | 256MB | 210MB/s | 180TB/year | 3 years | Faster 8TB NAS workloads |
| 10TB | IronWolf | ST10000VN000 | 7,200 | CMR | 256MB | 210MB/s | 180TB/year | 3 years | Bay-efficient home and small-office NAS |
| 12TB | IronWolf | ST12000VN0008 | 7,200 | CMR | 256MB | 210MB/s | 180TB/year | 3 years | Large media libraries and backups |
| 16TB | IronWolf | ST16000VN001 | 7,200 | CMR | 256MB | 240MB/s | 180TB/year | 3 years | Maximum current standard-family capacity |
| 12TB | IronWolf Pro | ST12000NT001 | 7,200 | CMR | 256MB | 255MB/s | 550TB/year | 5 years | Business NAS and heavier shared workloads |
| 14TB | IronWolf Pro | ST14000NT001 | 7,200 | CMR | 256MB | 255MB/s | 550TB/year | 5 years | Business NAS with moderate growth |
| 16TB | IronWolf Pro | ST16000NT001 | 7,200 | CMR | 256MB | 255MB/s | 550TB/year | 5 years | Heavy multi-user storage |
| 18TB | IronWolf Pro | ST18000NT001 | 7,200 | CMR | 256MB | 270MB/s | 550TB/year | 5 years | Dense business arrays |
| 20TB | IronWolf Pro | ST20000NT001 | 7,200 | CMR | 256MB | 285MB/s | 550TB/year | 5 years | High-capacity production NAS |
| 22TB | IronWolf Pro | ST22000NT001 | 7,200 | CMR | 512MB | 285MB/s | 550TB/year | 5 years | High-capacity production NAS |
| 24TB | IronWolf Pro | ST24000NT002 | 7,200 | CMR | 512MB | 285MB/s | 550TB/year | 5 years | Dense arrays with lower published acoustics |
| 24TB | IronWolf Pro | ST24000NT031 | 7,200 | CMR | 512MB | 240MB/s | 550TB/year | 5 years | Exact-model verification required |
| 28TB | IronWolf Pro | ST28000NT000 | 7,200 | CMR | 512MB | 270MB/s | 550TB/year | 5 years | Very dense commercial NAS |
| 30TB | IronWolf Pro | ST30000NT011 | 7,200 | CMR | 512MB | 275MB/s | 550TB/year | 5 years | Very dense commercial NAS |
| 32TB | IronWolf Pro | ST32000NT000 | 7,200 | CMR | 512MB | 285MB/s | 550TB/year | 5 years | Maximum tracked IronWolf Pro capacity |
Prices are entered by the user because marketplace prices change. The live offers section supplies fresh matching listings when the Cloudzat catalogue has them.
Live catalogue
Current IronWolf offers for RAID arrays
Only fresh, new-condition IronWolf and IronWolf Pro HDD offers from this plugin's dedicated catalogue are eligible. SSDs, enclosures, NAS appliances, SAS drives, multipacks and non-new listings are rejected.
Interactive decision tool
Calculate IronWolf RAID capacity and cost
Choose an exact tracked model or enter a custom drive capacity and price. The result provides simplified planning figures, not a vendor-specific format guarantee.
How the simplified RAID formulas work
For equal-size drives, RAID 0 and JBOD expose all raw capacity but provide no parity protection. RAID 1 mirrors data and normally exposes one member’s capacity. RAID 5 subtracts one member, RAID 6 subtracts two and RAID 10 exposes half the raw capacity.
These formulas are useful for comparing configurations. They do not represent every vendor’s hybrid RAID implementation, metadata reservation or expansion rule.
Decimal TB versus binary TiB
Drive manufacturers use decimal units: one terabyte is one trillion bytes. Many operating systems display binary tebibytes or label a binary calculation as TB. As a result, a newly installed drive appears numerically smaller even when no capacity is missing.
The calculator estimates TiB by converting the simplified decimal usable capacity. Formatting, file-system metadata and reserved system partitions reduce the final number further.
Minimum drive counts and invalid layouts
RAID 5 needs at least three drives, RAID 6 needs at least four and RAID 10 needs an even number of at least two. A one-drive volume may be labelled RAID 1 or hybrid RAID by some systems for future expansion, but it has no current disk-failure protection.
The calculator blocks invalid combinations so a capacity result is not shown for a layout that cannot be built as selected.
Cost per raw and usable terabyte
Raw price per terabyte divides total drive cost by all labelled capacity. Usable price per terabyte divides by the smaller RAID result. The second number is more relevant when comparing two protected arrays.
Include the cost of a hot or cold spare, taxes, the NAS enclosure and power if they materially affect the purchase. A seemingly cheap capacity can become expensive when it consumes every bay.
Network speed versus drive throughput
A single modern IronWolf drive can exceed a one-gigabit Ethernet link in sequential transfers. A multi-drive array can exceed faster links, but protocol overhead, CPU, encryption, file size and random access change real performance.
The calculator compares the selected network’s theoretical ceiling with the sum of official per-drive sustained specifications. The result is only a bottleneck indicator, not a benchmark promise.
Why reserve and snapshots are shown separately
Free-space reserve is capacity intentionally left available for stable operation and growth. Snapshot allowance represents retained changed data and version history. Combining them into one percentage can hide which policy is consuming the volume.
Review both after deployment. A snapshot policy can be shortened, while organic data growth may require additional drives.
RAID protects uptime, not every copy of data
RAID can keep a service available after selected drive failures. It cannot protect against accidental deletion, malware, theft, fire, controller failure or corruption replicated across the array. Seagate’s own RAID guidance recommends another storage device for backup.
The calculator displays a warning when no independent backup is selected. Treat that warning as a design issue, not a cosmetic message.
Use the result with the NAS vendor’s rules
Before buying, check supported capacities, exact models, expansion order, drive replacement instructions and whether the platform permits mixed sizes. Some systems require all members to be replaced before additional capacity becomes available.
Record the planned and actual results. A small difference after formatting is normal, while a large unexplained difference should be investigated before data migration.
How Cloudzat calculates IronWolf plans
Cloudzat uses simplified equal-drive RAID formulas for comparison: RAID 1 exposes one drive, RAID 5 subtracts one member, RAID 6 subtracts two, and RAID 10 exposes half the raw capacity. Manufacturer decimal terabytes are used first; binary TiB, file-system overhead, snapshots and reserved working space reduce what the operating system ultimately shows. Vendor hybrid RAID and migration behavior can differ.
Every product is treated by exact model where the identifier is available. The current tracked set includes standard IronWolf models from 2TB through 16TB and exact IronWolf Pro models from 12TB through 32TB. Live offers must be fresh, new-condition SATA IronWolf HDD listings. Calculators are planning aids, not compatibility guarantees, performance promises or replacements for backup.
Frequently asked questions
Seagate IronWolf planning questions
How much usable space does four 12TB drives in RAID 5 provide?
How much usable space does four 12TB drives in RAID 6 provide?
Why does a 12TB drive not show 12TB in the operating system?
Is RAID 10 always faster than RAID 6?
Can I use the calculator for Synology Hybrid RAID?
Does RAID replace backup?
Primary sources
- Seagate IronWolf current standard-family data sheet
- Seagate IronWolf Pro 12TB through 22TB data sheet
- Seagate IronWolf Pro 28TB, 30TB and 32TB data sheet
- Seagate explanation of RAID 0, RAID 1 and backup limits
Cloudzat may earn a commission from qualifying purchases. Product availability, pricing and specifications can change. Confirm the exact IronWolf model, seller, condition, regional warranty route and NAS compatibility before buying.