DAS Cost Calculator: Drives, RAID and Usable Storage
Build a complete direct-attached storage configuration using current eligible enclosure and internal-drive prices. Select a chassis, drive type, capacity, installed drive count and RAID level to estimate total cost and usable storage.
Use the calculator to compare complete system cost rather than buying the cheapest empty enclosure. It estimates raw and usable decimal terabytes, approximate tebibytes, fault tolerance, empty bays and cost per usable terabyte. Confirm that the selected enclosure supports the chosen RAID and number of drives.
Build a DAS configuration
Estimated configuration
How to use the DAS calculator
Select an enclosure from the current catalogue, then choose HDD or SSD, the drive capacity, number of installed drives and RAID level. The calculator uses the current eligible Amazon price for the enclosure and the lowest current new internal-drive offer at the selected capacity. It multiplies the drive price by the installed count and adds the chassis price.
The result is an estimate, not a checkout quote. Amazon prices and availability can change, and the selected enclosure may require a different drive form factor or paid RAID software. Open every shopping-list item and confirm the variant before ordering.
Raw capacity versus usable capacity
Raw capacity is the sum of the installed drive labels. Four 12TB drives provide 48TB raw. RAID consumes some capacity for mirrors or parity. Formatting and file-system metadata reduce the visible amount further. Operating systems may display tebibytes while manufacturers advertise decimal terabytes, so the number shown in the Finder or File Explorer is smaller.
The calculator reports both decimal usable TB and an approximate TiB conversion. It does not reserve vendor-specific system partitions because DAS controllers differ.
RAID capacity formulas
Individual, JBOD and RAID 0 use the combined capacity of all selected drives, although RAID 0 and JBOD have no drive-failure protection. RAID 1 uses about one drive worth of capacity. RAID 5 uses the capacity of all but one drive. RAID 6 uses all but two. RAID 10 uses half the raw capacity and requires an even number of drives.
These formulas assume matching drives. Mixed sizes normally calculate from the smallest member. Proprietary modes and expansion behavior can differ, so confirm the enclosure manual.
Fault tolerance is not data protection by itself
RAID 1 and RAID 5 can normally survive one failed drive. RAID 6 can survive two. RAID 10 can survive at least one and sometimes more if failures occur in different mirror pairs. RAID 0, JBOD and individual disks do not create array-level redundancy.
The fault-tolerance result covers drive failure only. It does not protect against deletion, ransomware, theft, fire, controller failure or file corruption. Include a separate backup destination in the real budget.
Cost per raw and usable terabyte
Cost per raw terabyte divides the complete enclosure plus drive cost by the sum of drive labels. Cost per usable terabyte divides by the RAID-adjusted capacity. A RAID layout with more protection usually raises the usable cost. This makes it easier to compare a cheap five-bay enclosure with a more expensive four-bay product and different drive sizes.
Do not select solely by the lowest cost. Warranty, cooling, interface, RAID utility and replacement-drive availability influence the true lifetime value.
Drive price and suitability
The calculator reads the existing Cloudzat storage catalogue for fresh internal HDD and SSD offers. For multi-bay HDD arrays, a NAS-class CMR model may be preferable to the absolute cheapest desktop drive. For SSD arrays, verify SATA or NVMe support, endurance and cooling. The lowest current offer is a price reference, not an automatic compatibility guarantee.
Matching models simplify RAID behavior. If a capacity has no fresh eligible drive price, run the main storage refresh or choose another size.
Enclosure limitations to confirm
The number of installed drives cannot exceed the physical bays. The selected RAID level must be supported by the enclosure or by a compatible host software layer. A non-RAID DAS can still use operating-system software RAID, but portability and recovery differ. Hybrid enclosures may allocate some bays to NVMe rather than SATA.
Check maximum drive capacity, host protocol, operating-system utility, power supply and whether the offer is diskless or populated.
Example planning decisions
A capacity-focused Plex server may prefer five large HDDs in RAID 5. A video editor may prefer four SATA SSDs in RAID 10 or RAID 0 with separate backup. A photographer may choose four HDDs in RAID 5 plus cloud or offline backup. A backup rotation may use individual disks rather than one array.
Run several configurations and compare total cost, usable capacity, empty bays and fault tolerance. The cheapest first purchase is not always the easiest system to grow or recover.
Using the estimate in a real purchase plan
After comparing configurations, add costs the calculator does not automatically include: a UPS, spare drive, replacement cable, paid RAID software, backup destination and any mounting adapters. For professional use, include the value of downtime and the time required to rebuild or restore the array. A system with a slightly higher purchase price can be cheaper over its life if support and recovery are clearer.
Save the chosen configuration before ordering and verify every Amazon variant. Marketplace listings can combine diskless enclosures and populated bundles under one page. Confirm bay count, included drives, power plug, warranty seller and RAID license in the cart. Recalculate if any price or model changes, because a different enclosure or drive can alter both compatibility and usable cost.
Quick decision guide
Capacity configuration
Compare larger HDDs and RAID 5 for lower cost per usable terabyte.
Performance configuration
Compare SATA SSDs, faster links and RAID 10 or RAID 0 with independent backup.
Growth configuration
Leave one or more bays empty only when the controller supports future expansion.
Safety configuration
Budget for a UPS, spare drive and separate backup, not only the enclosure and array members.
How Cloudzat builds this comparison
The calculator uses current eligible products already stored by Cloudzat. It does not call Amazon during page rendering. Capacity formulas are generic estimates, and manufacturer-specific implementation remains authoritative.
Technical content reviewed August 1, 2026. Manufacturer specifications and marketplace variants can change.
Frequently asked questions
Does the calculator include drives?
Yes. It adds the selected number of current internal-drive offers to the current enclosure price.
Why is usable capacity lower than raw capacity?
RAID redundancy, formatting and decimal-to-binary display differences reduce the visible amount.
Can I calculate RAID 5 with two drives?
No. RAID 5 requires at least three drives. The calculator warns when a layout is invalid.
Does the calculator guarantee compatibility?
No. Confirm the drive type, maximum size, RAID mode and exact product variant with the manufacturer.
Are prices cached?
The calculator reads the current Cloudzat catalogues and displays their checked time. Amazon prices can change after that time.
Does cost per usable TB include a backup?
No. Add the cost of a separate backup system to the complete storage budget.