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WD Blue vs. Black vs. Red & Purple HDD & SSD Differences

SSDs have continued to displace demand for HDDs, especially so in the consumer segment. As SSDs can now affordably and competitively fill the low-end storage needs for client PCs, OEMs, laptops, etc., HDD vendors are showing increasingly less interest in this area, meaning production for 500GB products is spinning down. Platter density has advanced to the point where it just isn’t practical or cost-effective to produce low capacity SKUs. 

Here are just a few of the HDDs we’ll be talking about today:


  • WD Black 6TB HDD & WD Black 2TB HDD 
  • WD Red 8TB HDD 
  • WD Purple 3TB 
  • WD Blue 2TB HDD & WD Blue 6TB HDD
  • Western Digital 4TB WD Red

WD Red vs. Blue vs. Black vs. Purple Comparison & Differences

Specifications WD Blue WD Black WD Red WD Purple
Capacity 500GB – 6TB 500GB – 6TB 750GB – 8TB 500GB – 8TB
Form Factor 3.5” 3.5” 3.5”/2.5” 3.5”
Transfer (Sustained) Up to 175 MB/s (6TB model) Up to 218 MB/s (6TB model) Up to 178 MB/s (8TB model) Up to 178 MB/s (8TB model)
Cache (MB) 32/64MB 64/128MB 16/64/128MB 64/128MB
RPMs 5400-7200 7200 5400 5400
Load/Unload Cycles 300,000 300,000 600,000 300,000
Warranty 2-year 5-year 3-year 3-year
Power in Watts (Read/Write/Idle) 5.3/3.4 (6TB, 5TB, 4TB), 4.1/3.0 (3TB, 2TB), 3.3/2.5 (1TB @5400RPM), 6.8/6.1 (1TB@7200RPM), 6.8/6.1 (500GB) 10.6/7.6 (6TB,5TB), 9.1/5.8 (4TB), 9.5/8.1 (3TB, 2TB), 6.8/6.1 (1TB, 500GB) 6.4/5.2 (8TB), 5.3/3.4 (6TB, 5TB), 4.5/3.3 (4TB), 4.1/2.7 (3TB, 2TB), 3.3/2.3 (1TB), 1.4/0.6 (1TB 2.5”, 750GB 2.5”) 6.4/5.7 (8TB), 5.3/4.9 (6TB, 5TB), 5.1/4.5 (4TB), 4.4/4.1 (3TB, 2TB), 3.3/2.9 (1TB, 500GB)
Acoustics in dBA (Idle/Seek) 25/28 (6TB, 5TB, 4TB), 23/27 (3TB, 2TB), 21/24 (1TB@5400RPM), 29/30(1TB@7200RPM), 29/30 (500GB) 31/34 (6TB,5TB), 29/36 (4TB), 29/34 (3TB,2TB), 29/30 (1TB,500GB) 20/29 (8TB), 25/28 (6TB, 5TB, 4TB), 23/34 (3TB, 2TB), 21/22 (1TB), 24/25 (1TB 2.5”, 750GB 2.5”) 20/29 (8TB), 25/26 (6TB, 5TB, 4TB), 23/24 (3TB, 2TB), 21/22 (1TB, 500GB)

D Blue Best Uses (Everyday computing, mainstream)

The WD Blue line is perhaps Western Digital’s bread and butter, aimed at mixing high capacity, fast sequential write/read speeds, and affordability. These drives are primarily aimed at everyday computing and basic media consumption; they are the jumping-off point for the average customer. Disconcertingly, WD Blue offers two spindle speeds: 5400RPM and 7200RPM. This is resultant of blending in the WD Green drive line. Any model number ending with a “z” is a former WD Green offering, and runs at 5400 RPMs.

The 1TB model is still the flagship performer, running at 7200 RPM and hosting 64MB of cache. In the past, Western Digital has used Marvell controllers and Samsung chips for the cache in this model. The WD Blue drives lack advanced features like vibration protection or TLER (RAID specific) and come with the lowest warranty at 2 years.

Generally, we’ve recommended WD Blues for primary drives and gaming use as they offer a nice cost-to-performance ratio in regards to capacity and speed.

WD Black Best Uses (Gaming, creative professionals, power users)

Western Digital’s designated Black series is comprised of the performance oriented consumer drives. WD Blacks are aimed at high capacity with the fastest possible throughput. Previously, a WD Blue or Green drive could prove to be a bit faster sequentially than a WD Black, primarily due to platter density. The newest 6TB WD Black aims to rectify this.

The 6TB flagship driveis made up of 5x 1.2 TB platters in addition to 10 read/write heads. This maximizes data density per platter and helps minimize the travel of the heads. The DRAM cache has also doubled from the previous 4TB predecessor, coming in at 128MB. Moreover, the Dynamic Cache Technology is intended to be more prescient with data requests and moving said data off the platters for theoretically quicker throughput. The cache is provided by NANYA, and the dual-core controller comes from LSI. Additionally, the firmware has seen tuning to improve sequential read/write performance.

WD Blacks forgo the energy and sound conscious features of the WD Blue series, but offer advanced vibration protection and the best available warranty of 5 years.

WD Red Best Uses (Network Attached Storage)

Although not for gaming, the commonness of home based cloud storage, SOHO environments, RAIDs, and server investments make the WD Red line worth mentioning. GN uses three WD Red 2TB disks for its own RAID 5 setup on its render machine, which we chose for their affordability, density, and reliability in RAID.

Distinguishing WD Reds from their desktop counterparts is that they are built to withstand the challenges of the always-on NAS environment. NAS drives are built to endure the constant vibrations and thermal envelope inherent to multi-drive systems.

Previously limited to a 6TB capacity, the WD Red line is headed by the newest 8TB model. Western Digital uses their HelioSeal technology to fill and seal the drive with helium. Helium is lighter than air, and its purpose is twofold: it allows the chassis to accommodate an extra 1.2 TB platter (7 total), and it allows for less turbulence and resistance equating to less power draw and heat. Observing the above table, users can see the WD Red series sport load/unload cycle ratings twice that of the other drives, offering a glimpse into the expected service life.

The WD Red 8TB uses 14 read/write heads, an LSI-based controller in conjunction with 128MB of cache, has RAID error recovery controls, NASware 3.0, and comes with a 3-year warranty.

WD Purple Best Uses (Surveillance, DVR, NVR)

WD Purple is Western Digital’s surveillance class storage. These drives are suited for 24/7 usage and the firmware and caching algorithms are optimized for write intensive applications, as these drives spend most their service life writing. illustrating the price/capacity focus of the Purple drives.

Exclusive to the WD Purple series is AllFrame technology. By reducing errors, pixilation and video interruptions, AllFrame attempts to reduce video frame loss. WD Purple also features TLER and support for the ATA streaming command set.

WD Purple drives can support up to 8 drive bays and 64 HD cameras, have an annualized workload of 180TB/year, and come with a 3-year warranty. Because these drives write and erase data endlessly, the higher annualized workload becomes important.

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