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Silver 3.5 inch internal hard drive with exposed circuit board on underside

Western Digital

Western Digital WD121KFBX 12TB 7200 RPM 256MB SATA 3.5" internal hard drive

SKU CH-E7B8-WZTCH MPN WD121KFBX

A 12 TB, 7200 RPM SATA desktop drive with 256 MB cache, built for multi-bay NAS systems

  • Total capacity12 TB
  • Interface typeSATA 6.0Gb/s
  • Form factor3.5 in (8.89 cm)
  • Flash memory typeHard Drive
  • Rotational speed7,200 RPM
  • Cache memory256 MB
  • 12TB capacity for large NAS arrays
  • 7200 RPM spindle speed for fast data access
  • 256MB cache to accelerate read and write operations
  • Supports up to 24 drive bays for scalable storage
  • 300TB per year workload rating for heavy NAS use

12TB SATA NAS drive

The WD Red Pro WD121KFBX is a 12TB 3.5-inch internal hard drive built for multi-bay NAS enclosures. It spins at 7200 RPM with a 256MB cache and connects through a SATA 6.0Gb/s interface. The drive supports workloads up to 300TB per year and includes NASware 3.0 technology for error recovery control.

Built for 1–24 bay NAS, not single-drive desktops

This drive suits administrators who need high-capacity storage in RAID or JBOD arrays of up to 24 bays. Its vibration management and extended testing target continuous operation in NAS appliances. Builders wanting a quiet desktop drive or a boot device for a single-bay PC should look elsewhere.

Fits standard 3.5-inch bays with SATA power and data

The unit measures 147mm long, 101.6mm wide and 26.1mm high, matching common 3.5-inch drive trays. It requires a SATA data cable and a SATA power connector from the host system. The 6W operating draw leaves headroom for multiple drives on a single power supply rail.

How it compares

Measured against everything we stock in 3.5-Inch Internal Desktop HDDs, at today’s prices. Recalculated every night.

Price $308.99
Pricier than about 83% of the 4,938 comparable items (median $107.99).
Total capacity 12 TB
Higher than about 90% of the 2,372 comparable items (median 2 TB).
Price per TB $25.75 per TB
Cheaper than about 88% of the 2,365 comparable items (median $62.21 per TB).

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Specifications

Product
Brand nameWD
Product lineRed Pro
Model nameWD121KFBX
Total capacity12 TB
Recommended useEnterprise NAS Hard Drives
Performance
Rotational speed7,200 RPM
Storage
Flash memory typeHard Drive
Cache memory256 MB
Ports & slots
Interface typeSATA 6.0Gb/s
Size & build
Form factor3.5 in (8.89 cm)
Max height26.1 mm
Maximum width101.6 mm
Maximum length147 mm
Shipping weight0.77 kg
Package size231 × 152 × 79 mm

Questions about this item

Does this 3.5" 12TB drive need a SATA power cable and a SATA data cable to operate?

Yes, the drive uses a standard SATA 6.0Gb/s interface and requires both a SATA data cable from the host and a SATA power connector from the power supply.

Can this 7200 RPM Red Pro drive share a NAS with slower existing drives?

The drive spins at 7200 RPM with a 256MB cache and supports up to 24 bays, so it can operate in the same enclosure as drives of different speeds.

How do I confirm the 12TB Red Pro is healthy after installation?

Check that the system BIOS or NAS OS detects the full 12TB capacity at SATA 6.0Gb/s, then run the built-in SMART self-test and verify zero reallocated sectors.

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