WD Red 6TB full review

WD Red

As inevitable as death and taxes, the size of hard disks is always changing, getting bigger by the year. We were at a 4 TB impasse for a while though, since late in 2011 when first Seagate and closely followed by Hitachi, released the first 3.5-inch SATA disks with 4000 GB of storage capacity. Also see: Best NAS drives.

Much has changed in the world of storage since 2011, with Hitachi's entire disk-making division bought out by Western Digital, and Toshiba encouraged to expand beyond its 2.5-inch comfort zone into 3.5-inch products. That move was inspired by Chinese monopolies investigators' concerns, in order to reduce the duopoly of otherwise the only two 3.5-inch hard-disk makers still left standing – Seagate and WD.

Additionally in the three years since 2011, solid-state storage has encroached even more into traditional disk-based products like laptops and desktop PCs. But for bulk storage of the kind you'd leave at home, work or in the datacentre, the big hard disk still has a key job to do.

WD has poured its disk knowledge and manufacturing talents into two new super-sized HDDs, using its popular WD Red range as the vehicle. Now we have 5 TB and a 6 TB capacity options added to this NAS-oriented disk series. See all NAS drive reviews.

WD Red 6 TB: Design and Features

The WD Red 6 TB then is the largest commercially available hard disk in the world right now, using five platters that each store 1200 GB of data – in other words, 600 GB on each side of each mirror-like spinning circular wafer.

Besides the 50 percent increase in total capacity over the formerly largest 4 TB drive, WD has made some other changes. The firmware that runs the storage show for each disk has been honed to a new version, known as NASware 3.0. This on-board software is responsible for controlling the motor and read/write heads, and although the specifics are not detailed the newer firmware is said to now support features like ATA Streaming Feature Set, useful for AV storage programs like Windows Media Center. SMART Command Transport (SCT) is supported for monitoring drive health more closely, with temperature accuracy now given as to within 1 degree celsius.

Drive reliability is also billed as improved, along with optimised power usage – a crucial area for these network-storage disks that already take various measures to reduce energy consumption in their typical always-on 24/7 environment.

The refinement of the firmware may be one reason why WD will now certify the WD Red disk range for use in NAS boxes with up to eight bays – hitherto a six-disk maximum was recommended, due to vibrational issues when too many disks are spinning at once. Too much mechanical motion from spinning platters has been known to increase the chance of each disk's read/write head from mistracking and having to re-read sectors, slowing down performance.

The rotational speed remains ‘IntelliPower', which is WD marketing speak for ‘something sub-6000 rpm that we'd rather not publish'. But where our graphed performance output of the 3 TB version suggests a step change in rotational speed, leading to sawtooth changes in read/write speed, the new 6 TB disk showed a slightly more linear, consistent result across the drive's entire capacity.

In other respects, the specifications are the same as earlier WD Red disks, a 64 MB memory buffer, and SATA Revision 3 (6 Gb/s) interface. The warranty period is also the same, at three years; and the mean-time between failure (MTBF) rating remains at 1,000,000 hours.

At around £210 the disk is not cheap, but on a cost per capacity basis it looks more attractive – just 3.5p per gigabyte. That makes it a little more expensive than the 4 and 3 TB versions, currently at around 3.1 and 2.9p per gigabyte, although the flagship biggest disks are often priced higher in these terms; initially at least.

WD Red 6 TB: Lab results

As hard-disk capacity increases, so too typically does areal density – the number of bit packed into each square unit of area. Consequently it's not unexpected for performance to increase with capacity – and that's what we did find at one end of the performance chart with the WD Red 6 TB.

Using the simple ATTO Disk Benchmark test, this disk reached up to 188 MB/s in sequential reads, and 175 MB/s in sequential writes. That's impressively quick for a single hard disk.

Down at the small-file level though, newfound capacity also brought with it a drop in performance. Take 1 kB files for example.

With the 3 TB WD Red we recorded reads and writes at around 32 and 23 kB/s respectively. The 6 TB disk meanwhile could manage 69 kB/s for its disk writes; but a meager 104 B/s (yes, bytes per second) when tasked with reading these smaller files.

Turning to CrystalDiskMark we had a retelling of the same kind of story. At its peak, the disk could read and write at 175 MB/s, which compares well with the 3 TB version which we measured with 163 and 169 MB/s. With 512 kB data the two capacities had a similar write speed (97 MB/s for 3 TB; 92 MB/s for 6 TB). But read speeds here had already diversified, to 48 MB/s for 3 TB but just 23 MB/s for 6 TB. And again, at the 4 kB level, the larger disk had around half the read speed: 252 kB/s versus 582 kB/s for 3 TB disk.

From HD Tune Pro we also noted a shift in access times. The 3 TB disk measured with 22.2 and 18.6 ms latency for reads and writes respectively. The 6 TB disk reordered its ranking with 18.5 and 26.4 ms latencies. These are not the quickest results but they also don't suggest a dramatic loss in access time when compared to most 3.5-inch SATA disks. Also see: Best NAS drives.


WD Red 6TB: Specs

  • 6 TB hard disk
  • 3.5in SATA Revision 3 HDD
  • 64 MB cache
  • ‘IntelliPower' rotation speed
  • NASware 3.0 firmware
  • 3-year warranty
  • 1,000,000 MBTF rating
  • 25/28 dB idle/seek acoustic noise
  • 147 x 101.6 x 26.1 mm
  • 750g

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