Western Digital WD Red Pro 4TB NAS Hard Drive: features, specs and who it suits

The Western Digital WD Red Pro 4TB (model WD4003FFBX) is an internal 3.5-inch hard drive made for network attached storage, or NAS. A NAS is a small box of drives that sits on your network and shares files, backups and archives with several people or devices. This drive is meant to be one of the disks inside it, running day and night.

What "NAS drive" means

A drive in a NAS behaves differently from one in a desktop PC. It stays powered on for long stretches, sits right next to other spinning drives, and works as part of a RAID array, where several disks share the job of storing data so that one failure doesn't lose everything. Western Digital positions the Red Pro for medium and large business use and says it is available for NAS systems of up to 24 bays. The listing also mentions use in personal setups, so it isn't limited to offices.

CMR, 7200 RPM and cache

The drive spins at 7200 RPM, which is the faster of the two common speeds for 3.5-inch disks, and it carries 256 MB of cache. It uses CMR (conventional magnetic recording). In general, CMR writes each track separately, which tends to give steadier performance during long writes and when a RAID array rebuilds, compared with shingled recording (SMR), where tracks overlap. For NAS work that steadiness is usually the point of choosing CMR.

The interface is SATA 6 Gb/s, the standard connection for 3.5-inch drives. The listing gives a data transfer rate of 750 megabits per second, and notes that real-world speed in a NAS is usually limited by the network and the number of drives working together.

Reliability features

Western Digital lists several features aimed at keeping an array healthy:

• NASware 3.0 firmware, which it describes as providing error recovery controls. In a RAID, a drive that spends too long retrying a bad sector can get dropped from the array, so limiting that retry time is a common NAS feature.
• 3D Active Balance Plus, which the brand says helps with vibration and balance.
• Vibration and shock protection, which matters when many drives spin in one enclosure.
• Extended testing, with each drive tested for extended operation, according to the brand.

Together with RAID error recovery control, these are designed to reduce failures within the NAS system, as Western Digital puts it. The drive carries a five-year limited manufacturer's warranty.

Size and fit

The drive measures about 5.8 x 4.0 x 1.0 inches (roughly 14.7 x 10.2 x 2.5 cm) and weighs 1.6 lb (about 0.73 kg). That is the standard 3.5-inch form factor, so it slots into NAS bays and desktop drive cages made for that size.

Who it suits

It is aimed at people building or expanding a multi-bay NAS for shared files, archiving and backups, particularly when the array will run continuously. Someone who needs a single disk for an occasional desktop backup may not need the extra NAS features.

What to check before you buy

• Confirm that your NAS or server lists 3.5-inch SATA drives and has a free bay.
• Check the NAS maker's compatibility list for this model.
• Make sure the capacity suits your needs, and consider the RAID level you plan to use, since redundancy reduces usable space.
• Plan for power and airflow, since several 7200 RPM drives produce heat and some noise.
• Keep separate backups. RAID protects against a drive failure, but it isn't a backup.

The short version

• A 4TB, 3.5-inch, 7200 RPM CMR hard drive with 256 MB cache and SATA 6 Gb/s.
• Western Digital designed it for NAS systems of up to 24 bays and 24x7 use.
• NASware 3.0 error recovery and vibration protection target RAID use.
• Five-year limited manufacturer's warranty.
• Standard 3.5-inch size; check your NAS compatibility list first.

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