WD Red Pro 16TB NAS Hard Drive (WD161KFGX): features, specs and who it suits

The WD Red Pro 16TB (model WD161KFGX) is a 3.5-inch internal hard drive made for network-attached storage. Western Digital designs the Red Pro line for NAS enclosures that run all day and are used by several people at once, such as a small office file server or a home lab that holds backups and media. This page explains what the main specs mean and what to confirm before adding one to a NAS.

What makes a NAS drive different

A desktop drive is usually built for a few hours of use at a time. A NAS drive spends its life spinning, serving files to several devices while it sits in an enclosure alongside other drives. Western Digital says the Red Pro is designed for the demands of high-intensity, 24x7, multi-user environments and for RAID-optimised systems. In general, drives sold for this job add firmware tuned for RAID behaviour and are built to cope with the vibration of neighbouring drives.

CMR, 7200 RPM and the 512 MB cache

Three specs shape how the drive behaves:

• CMR (conventional magnetic recording) writes data in separate, non-overlapping tracks. Typically, CMR drives keep steady write speeds under sustained workloads and during RAID rebuilds, which is why many NAS builders look for it.
• 7200 RPM is a faster spin speed than the 5400 RPM common in lower-power drives. Faster spinning generally means quicker access to data, though it usually comes with a little more heat and noise.
• 512 MB of cache is memory on the drive that buffers data on its way to and from the platters.

The interface is SATA 6 Gb/s, the standard connection for 3.5-inch drives in NAS bays and desktop PCs. Western Digital lists the drive at about 1.0 x 5.8 x 4.0 inches (roughly 2.5 x 14.7 x 10.2 cm) and 1.5 lb (about 0.7 kg).

The 550TB/yr workload figure

Western Digital rates the Red Pro for a workload of 550TB per year. That figure is the total data read and written in a year, scaled to the hours the drive was powered on, and the brand specifies it at a typical temperature of 40°C. Real workloads depend on your hardware, software and configuration. For many households and small offices, 550TB a year is far more than they would ever transfer, but it matters for busy servers.

Scale: up to 24 bays and RAID rebuilds

The company says Red Pro drives suit NAS systems with up to 24 bays and an unlimited number of bays in RAID-optimised setups. It also points to archiving, file sharing and RAID array rebuilds on file systems such as ZFS. During a rebuild, every remaining drive reads its full contents, so a drive that handles sustained load is useful. Capacities in the range run from 2 to 22TB; this model is 16TB. The listing notes that 1TB is counted as one trillion bytes, so the space your operating system reports will be somewhat lower.

Compatibility testing

Western Digital says it works with a wide range of NAS vendors to test compatibility with most NAS enclosures. As ever, it is worth looking at your NAS maker's own compatibility list for the specific model.

What to check before you buy

• That your NAS or server has a free 3.5-inch bay with a SATA connection.
• Whether your NAS vendor lists this model as compatible, and the maximum drive size it supports.
• Whether the drives in an existing array should match in model or recording type, since mixing can affect behaviour.
• Cooling and noise: a 7200 RPM drive is typically warmer and louder than a slower one, so consider where the enclosure sits.
• Backups: RAID protects against a drive failing, but it isn't a backup of your data.
• Warranty terms for your region, as set out by the manufacturer.

The short version

• A 16TB, 3.5-inch, 7200 RPM SATA 6 Gb/s hard drive with 512 MB of cache and CMR recording.
• Rated by Western Digital for a 550TB/yr workload and 24x7 multi-user NAS use.
• Aimed at RAID NAS systems, including larger arrays of up to 24 bays.
• Check bay type, vendor compatibility and cooling before installing.

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