# Western Digital WD Red NAS 4TB SATA 3.5" Internal Hard Drive with 5400 RPM & 256MB Cache

- Category: Storage
- Brand: Western Digital
- Model: WD Red NAS 
- Part number: WD40EFAX
- Price (US): $285.99
- Price last checked: 2026-08-06
- Rating: 4.6/5 from 1764 Amazon reviews
- Warranty: 3 years
- Product page: https://buildmypc.net/component-details/storage/western-digital-wd-red-nas-wd40efax/

## Description

n/a

## Specifications

| Spec | Value |
| --- | --- |
| Brand | Western Digital |
| Model | WD Red NAS  |
| Maximum Capacity | 4 TB |
| Form Factor | 3.5" (HDD) |
| Cache Memory | 256 MB |
| Interface | SATA 6 Gb/s |

## Key Features

- Specifically designed for use in NAS systems with up to 8 bays
- Supports up to 180 TB/yr workload rate Rate is defined as amount of user data transferred to or from drive. Workload Rate is annualized (TB transferred times (8760/recorded power-on hrs)). Workload Rate will vary on hardware/software components
- NASware firmware for compatibility
- Small and home office NAS systems in a 24/7 environment
- 3-year manufacturer's limited

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