Direct-Attached Storage Benchmarks

Our evaluation routine for hard-drive based direct-attached storage devices involves running CrystalDiskMark for a quick performance overview. Real-world performance testing is done with our custom test suite involving robocopy bencharks and PCMark 8's storage bench. The host is a Thunderbolt 3 port enabled by the Alpine Ridge controller in the Hades Canyon NUC.

CrystalDiskMark uses four different access traces for reads and writes over a configurable region size. Two of the traces are sequential accesses, while two are 4K random accesses. Internally, CrystalDiskMark uses the Microsoft DiskSpd storage testing tool. The 'Seq Q32T1' sequential traces use 128K block size with a queue depth of 32 from a single thread, while the '4K Q32T1' ones do random 4K accesses with the same queue and thread configurations. The plain 'Seq' traces use a 1MiB block size. The plain '4K' ones are similar to the '4K Q32T1' except that only a single queue and single thread are used.

Comparing the '4K Q32T1' and '4K' numbers can quickly tell us whether the storage device supports NCQ (native command queuing) / UASP (USB-attached SCSI protocol). If the numbers for the two access traces are in the same ballpark, NCQ / UASP is not supported. This assumes that the host port / drivers on the PC support UASP. Things don't really start off well for the WD My Passport 5 TB - in the sequential access traces typically processed on external hard drives, the My Passport scores consistently less than the Seagate Backup Plus Portable - ~125 MBps vs. ~150 MBps. Like the previous generation My Passport (2016), the new one doesn't seem to support UASP or NCQ (despite CrystalDiskInfo claiming otherwise).

HDD-Based Direct-Attached Storage Benchmarks - CrystalDiskMark

Moving on to the real-world benchmarks, we first look at the results from our custom robocopy test. In this test, we transfer three folders with the following characteristics.

  • Photos: 15.6 GB collection of 4320 photos (RAW as well as JPEGs) in 61 sub-folders
  • Videos: 16.1 GB collection of 244 videos (MP4 as well as MOVs) in 6 sub-folders
  • BR: 10.7 GB Blu-ray folder structure of the IDT Benchmark Blu-ray (the same that we use in our robocopy tests for NAS systems)

The test starts off with the Photos folder in a RAM drive in the testbed. robocopy is used with default arguments to mirror it onto the storage drive under test. The content on the RAM drive is then deleted. robocopy is again used to transfer the content, but, from the storage drive under test to the RAM drive. The first segment gives the write speed, while the second one gives the read speed for the storage device. The segments end with the purge of the contents from the storage device. This process is repeated thrice and the average of all the runs is recorded as the performance number. The same procedure is adopted for the Videos and the BR folders.

Photos Read


High-performance external storage devices can also be used for editing multimedia files directly off the unit. They can also be used as OS-to-go boot drives. Evaluation of this aspect is done using PCMark 8's storage bench. The storage workload involves games as well as multimedia editing applications. The command line version allows us to cherry-pick storage traces to run on a target drive. We chose the following traces.

  • Adobe Photoshop (Light)
  • Adobe Photoshop (Heavy)
  • Adobe After Effects
  • Adobe Illustrator

Usually, PC Mark 8 reports time to complete the trace, but the detailed log report has the read and write bandwidth figures which we present in our performance tables. Note that the bandwidth number reported in the results don't involve idle time compression. Results might appear low, but that is part of the workload characteristic. Note that the same CPU is being used for all configurations. Therefore, comparing the numbers for each trace should be possible across different DAS units.

Adobe Photoshop Light Read

In our real-world benchmarks, the WD My Passport comes out on top consistently across almost all of the different workloads. While instantaneous performance for short-burst workloads favors the Seagate Backup Plus Portable, the WD My Passport is better for transferring tens of GBs of data in one go. Given that both of the 5TB models employ SMR platters, we got interested in figuring out how WD's SMR implementation compares against Seagate's for the external hard-drive use-case.

Introduction and Product Impressions Performance Consistency - Handling SMR Quirks
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  • MDD1963 - Sunday, October 6, 2019 - link

    Don't mind that insignificant 57.8% price difference!
  • zamroni - Tuesday, October 8, 2019 - link

    i prefer standalone case rather than built-in disk+case. it's more durable than built-in case+disk products.
    i had broken toshiba external disk which the pcb dead. i couldn't reuse any of it because the usb port is soldered into disk's pcb
  • Chloiber - Thursday, October 10, 2019 - link

    We're calling external harddisks 'DAS' now?
  • danwat1234 - Friday, May 21, 2021 - link

    It's too bad you did not measure the power consumption at idle! Going to be used a Western Digital passport for a Chia farming in which it will be almost the time..
  • danwat1234 - Friday, May 21, 2021 - link

    * idle most of the time

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