WD My Book Duo (2017) DAS Review

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Performance Testing & Conclusion

Comparison Products

There are a lot of options for desktop direct attached storage (DAS) products. There are single, dual, and even multi-drive products available, and many of them are very good. This product category also has a number of connectivity options. USB 3.x and Thunderbolt are the two dominant technologies. USB is in every system dating back a decade or more, while Thunderbolt has a limited install base. Later this year Intel will increase the install base of Thunderbolt 3 with the next generation processor and chipset combination that brings the technology to the processor level.

Western Digital has offered the My Book series for several years. The My Book VelociRaptor Duo was easily the most exciting model. It came armed with two 1TB 10,000 RPM platter speed drives and was the first My Book to use a Thunderbolt interface. We've included the My Book VelociRaptor Duo in our review along with the 3rd generation My Book (a single drive model).

We also included the Seagate Innov8 8TB and Seagate Backup Plus 8TB single drive DAS solutions.

Block Size Testing

In this test, we examine read and write performance with different transfer sizes. This is very similar to the ATTO Benchmark, but we use a queue depth (QD) of 1 instead of the ATTO's default QD4 setting. The new My Book Duo pushes the performance to nearly 400 MB/s. That's nearly twice as fast as the older My Book VelociRaptor Duo with the Thunderbolt interface. You also get a 10x capacity increase.

My Book Duo users won't see a performance increase with smaller transfers, so don't expect a boost in random performance with a dual-drive RAID configuration.

Full LBA Span Performance

We read and write 128KB blocks across the entire usable LBA range to measure sequential performance. The new My Book Duo 20TB delivers a very large performance increase compared to the other products. This illustrates the performance difference between a single and dual-drive configuration. Our sequential read test leads us to believe the system is limited by the USB 3.1 Gen 1 interface. USB 3.1 Gen 1 gives you the same 5Gbps speed as USB 3.0.

The sequential write test was much different than we expected. We ran the test three times and came away with similar results each time. The performance is less consistent than we expect to see from a dual drive array, and it breaks the typical downward performance curve.

File Transfers

We don't run many application tests on external or portable storage products because the typical workload is sequential in nature. Most of us simply read and write large pieces of data for archiving or transferring data from one location to another.

We often see performance measured in throughput, but time-based results are easier to interpret because the sense of time is universal. We tested transfer performance with a Blu-ray ISO. For the Game test, we used rFactor to transfer data from the post-installation directory to the portable drives. The Directory Test is a 15.2GB block of data that contains a mix of images, software installations, ISO files, and multimedia.

The odd performance from the sequential write test carries over to the file transfer test. We expected the 2017 My Book Duo to rip through our tests and leave the single drive and older products behind in a cloud of dust. That simply didn't happen. We ran the drive through three iterations of each file transfer and averaged the results. Furthermore, it wasn't a single result that threw the results off. All three iterations of the test were consistently within 1 second of each other.


The My Book Duo doesn't have a lot of competition in the market. The 20TB model we tested with two 10TB Red series HDDs costs roughly $850. Two Red 10TB drives alone cost $760 at Newegg, and even more at Amazon. It's possible to purchase an empty two-bay enclosure for $90, but $90 doesn't give an outside company enough room for packaging, cables, warranties, support staff, marketing, insurance, and everything else involved with running a modern-day technology company. A decade ago this was a thriving market, but consolidation has thinned the herd.

There are three main players in the pre-populated external enclosure market, and the HDD companies own all three. LaCie is now part of Seagate, G-Technology is part of Hitachi (a WD company), and Western Digital operates under its own brand name. The My Book Duo has a distinct price advantage over competing products from these companies. G-Technology has a G RAID 20TB box for $1,349.95, and LaCie has the 2big Dock Thunderbolt 3 20TB that retails for $1,299. The $849 My Book Duo 20TB comes out as the bargain of the group.

With such a large price disparity, you wouldn't think WD also leads the group in value-add software features. The software package isn't exclusive to the My Book product line, but it's impressive none the less. The company put a lot of effort into building a comprehensive package that offers real value to several different use-cases, from casual to professional.

The My Book Duo is more consumer than prosumer like the LaCie and G-Technology products. Western Digital chose to outfit this system with standard Red, and not Red Pro, HDDs. The tradeoff for the lower price is slightly lower performance and less consistency due to the slower platter speeds.

We would like to see the My Book Duo ship with USB 3.1 Gen 2 to increase the bandwidth for the two USB 3.0 ports. Unfortunately, when you use the ports to transfer data you also eat into the available storage bandwidth. You won't notice any performance degradation with low bandwidth devices, like keyboards, but if you use the ports for removable storage, like high-speed SD or Compact Flash cards, there will be a penalty depending on how fast your cards are.


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Chris Ramseyer
Chris Ramseyer is a Contributing Editor for Tom's Hardware US. He tests and reviews consumer storage.
  • derekullo
    I love Western Digital but seriously ...

    How does one screw up the performance in a raid 0?

    The blu-ray transfer looks great, but the Game Directory Transfer and Backup Directory tests look terrible.

    And that was after seeing the device crush everything else in the Sequential Read and Write benchmarks.

    Is there a reason for this "odd write performance".
  • yorich
    "improved raid controller silicon" . right... because RAID 0/1 requires so much horsepower. RAID controllers in anything but RAID5 do nearly nothing. And R5 in these types of enclosures is a turd at best.
  • elbert
    With 4TB hard drive capacity turning 8 this year I find that price to be extreme. The 2TB drives used are decade old capacity. I get HD makers had the flood in 2012 that destroied a lot of costly equipment. I even get they hit a hard wall capacity wise to get past. At this point tho they should be looking at quanity sales Its a step in the right direction with 2 drives but price is a bit beyond reason.