WD Red Plus 4TB NAS Hard Drive (WD40EFPX) – 5400 RPM, CMR, 256MB Cache

WD Red Plus 4TB NAS Hard Drive (WD40EFPX) – 5400 RPM, CMR, 256MB Cache

If you’re picking storage for a NAS system, the WD Red Plus 4TB (WD40EFPX) is one of Western Digital’s newer drives built specifically for that job. It’s a 3.5″ internal hard drive designed to run continuously inside a NAS enclosure, whether that’s a home media server or a small-office file share.

Built for always-on NAS storage

Regular desktop drives aren’t designed to spin 24/7. The WD40EFPX is, which is the whole point of the WD Red Plus line. It’s rated for use in NAS systems with up to eight bays, and it’s built to work well inside a RAID array alongside other drives, rather than as a single standalone disk.

It uses CMR (conventional magnetic recording), not SMR. This matters most during RAID rebuilds and sustained writes, where CMR drives tend to behave more predictably than SMR ones.

What makes the EFPX version different

This particular model carries a 256MB cache, a notable step up from the 64MB cache on the older WD40EFRX. A larger cache can help with buffering data during read/write operations, which is useful in busier NAS setups with multiple users or simultaneous tasks.

Spec Detail
Capacity 4TB
Form factor 3.5″ internal HDD
Interface SATA 6Gb/s
Speed class 5400 RPM
Cache 256MB
Recording technology CMR
Model number WD40EFPX
Who this drive fits
Home NAS and media enthusiasts: Central storage for movies, photos, and backups, streamable to any device on the network.
Photographers and content creators: A dependable spot for large media libraries and project files.
Small businesses and office IT admins: Shared storage and scheduled backups without enterprise pricing.
System builders: A CMR drive suited to RAID 1, 5, or 6 configurations.
Things worth knowing

The 5400 RPM speed class keeps power draw, heat, and noise lower than faster desktop drives, which matters if the NAS sits in a living room or small office. It won’t out-benchmark a 7200 RPM drive, but in most home and office networks, the network connection is the bottleneck, not the drive.

As with any drive, RAID redundancy isn’t a substitute for backups. If the data matters, keep a separate copy somewhere else too.

For most home and small-office NAS builds, the WD40EFPX is a solid, low-drama choice, and the larger cache makes it a reasonable pick if your NAS handles multiple users or heavier day-to-day use than a basic media box.

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