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Silver 3.5 inch internal hard drive with green label

Western Digital

Western Digital WD40EFPX 4TB 3.5" 5400 RPM 256MB CMR SATA internal hard drive

SKU CH-SAPA-CYYHA MPN WD40EFPX

4TB 3.5" CMR drive built for 24/7 NAS workloads up to 180 TB/yr with 256MB cache

  • Total capacity4 TB
  • Interface typeSATA 6.0Gb/s
  • Form factor3.5 in (8.89 cm)
  • Flash memory typeHard Drive
  • Recording methodCMR
  • Rotational speed5,400 RPM
  • 4TB capacity stores large media libraries and backups
  • CMR technology delivers consistent write performance for RAID arrays
  • 256MB cache accelerates frequent read and write operations
  • NASware firmware optimises drive behaviour for 24/7 NAS workloads
  • 180 TB/yr workload rating supports heavy multi-user environments

Purpose-built NAS storage

The WD Red Plus WD40EFPX is a 4TB 3.5-inch hard drive designed for small to medium business NAS systems that operate continuously. Its CMR recording technology and 256MB cache support multi-bay enclosures up to eight drives, delivering the capacity and reliability needed for always-on data protection and sharing.

SATA integration for RAID arrays

The drive connects through a SATA 6.0Gb/s interface and fits standard 3.5-inch bays with maximum dimensions of 147.00mm length, 101.60mm width and 26.10mm height. NASware™ firmware tunes drive parameters for RAID-optimised workloads, while extensive vendor testing ensures compatibility across most NAS enclosures without requiring additional configuration.

Efficient 24/7 operation

Engineered for a 180 TB/yr workload rate, the 5400 RPM spindle speed helps reduce power consumption and heat output compared with previous models. Lower operating temperatures contribute to quieter performance in thermally constrained chassis, supporting dependable long-term operation in systems that run 24 hours a day.

How it compares

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

Price $109.99
Typical for this category: the median of 4,938 items is $107.99.
Total capacity 4 TB
Higher than about 70% of the 2,372 comparable items (median 2 TB).
Price per TB $27.50 per TB
Cheaper than about 86% of the 2,365 comparable items (median $62.21 per TB).

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Specifications

Product
Brand nameWD
Product lineRed Plus
Model nameWD40EFPX
Total capacity4 TB
Recommended useFor NAS systems
Performance
Rotational speed5,400 RPM
Storage
Flash memory typeHard Drive
Recording methodCMR
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 weight0.54 kg
Package size146 × 102 × 25 mm

Questions about this item

What workload rate can the WD40EFPX sustain in a NAS before hitting its annual limit?

The drive is rated for up to 180 TB per year, which is the workload ceiling Western Digital specifies for this model in multi-bay NAS enclosures.

How much heat and noise should I expect when the drive runs 24/7 in a small NAS?

WD Red Plus drives are engineered to use less power and run cooler than prior models, reducing heat buildup and acoustic output during continuous operation.

Which NAS enclosures is this 3.5-inch SATA drive compatible with?

Western Digital tests the drive with a wide range of NAS vendors to ensure compatibility with most multi-bay enclosures that accept 3.5-inch SATA drives.

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