AnandTech DAS Suite - Benchmarking for Performance Consistency

Our testing methodology for DAS units takes into consideration the usual use-case for such devices. The most common usage scenario is transfer of large amounts of photos and videos to and from the unit. Other usage scenarios include the use of the DAS as a download or install location for games and importing files directly off the DAS into a multimedia editing program such as Adobe Photoshop. Some users may even opt to boot an OS off an external storage device.

The AnandTech DAS Suite tackles the first use-case. The evaluation involves processing three different workloads:

  • 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

Each workload's data set is first placed in a 25GB RAM drive, and a robocopy command is issued to transfer it to the DAS under test (formatted in NTFS). Upon completion of the transfer (write test), the contents from the DAS are read back into the RAM drive (read test). This process is repeated three times for each workload. Read and write speeds, as well as the time taken to complete each pass are recorded. Bandwidth for each data set is computed as the average of all three passes.

Blu-ray Folder Read

It can be seen that there is no significant gulf in the numbers between the different units. For all practical purposes, the casual user will notice no difference between them in the course of normal usage.However, power users may want to dig deeper to understand the limits of each device. To address this concern, we also instrumented our evaluation scheme for determining performance consistency.

Performance Consistency

Aspects influencing the performance consistency include SLC caching and thermal throttling / firmware caps on access rates to avoid overheating. This is important for power users, as the last thing that they want to see when copying over 100s of GB of data is the transfer rate going down to USB 2.0 speeds.

In addition to tracking the instantaneous read and write speeds of the DAS when processing the AnandTech DAS Suite, the temperature of the drive was also recorded at the beginning and end of the processing. In earlier reviews, we used to track the temperature all through. However, we have observed that SMART read-outs for the temperature in NVMe SSDs using USB 3.2 Gen 2 bridge chips end up negatively affecting the actual transfer rates. To avoid this problem, we have restricted ourselves to recording the temperature at either end of the actual workloads set. The graphs below present the recorded data.

Performance Consistency and Thermal Characteristics

The first three sets of writes and reads correspond to the photos suite. A small gap (for the transfer of the video suite from the internal SSD to the RAM drive) is followed by three sets for the video suite. Another small RAM-drive transfer gap is followed by three sets for the Blu-ray folder. An important point to note here is that each of the first three blue and green areas correspond to 15.6 GB of writes and reads respectively. Of all the tested drives, only the Crucial Portable SSD X8 hiccups a little during certain writes. Temperature-wise, the OWC Envoy Pro EX USB-C and the Samsung T7 Touch both show only a 3C increase in temperature on eithe side of the workload. On the other hand, the Lexar SL100 Pro shows a significant 11C increase, pointing to possible thermal issues in the long run.

Synthetic Benchmarks - ATTO and CrystalDiskMark PCMark 10 Storage Bench - Real-World Access Traces
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  • lilkwarrior - Thursday, January 23, 2020 - link

    Seems pointless to not be Thunderbolt 3 or USB4.
  • avbohemen - Thursday, January 23, 2020 - link

    I wonder what the limit is in the atto/as-ssd iops test. All drives hit a limit of 23-25k 4kB iops (atto) or 32k 4kB iops (as-ssd).

    Throughput is not saturated with 4kB iops and the drives are different enough in other benchmarks.

    Is it a limitation of the usb/uasp protocol or the bridge chip, or something else?
  • avbohemen - Thursday, January 23, 2020 - link

    Sorry, I mean crystaldiskmark instead of as-ssd.
  • Soulkeeper - Thursday, January 23, 2020 - link

    The crucial looked like the winner untill I saw the Performance Consistency results. Horrible.
    Otherwise most the benchmark results, outside of this, seem very close for all the drives to me.
  • ganeshts - Friday, January 24, 2020 - link

    Exactly! And, dare I say, for most casual users, the Crucial drive actual works out well. It is only power users and tech-savvy folks who expect to 'torture' their external drives that need to watch out :) Unlike other review sites [ and I don't want to name any ;) ], our aim is to give the complete picture so that readers can make an informed purchase decision.

    To be honest, if I were to purchase a portable SSD for occasional periodic backups (say, 10 - 20 GB of data at a time), the X8 is actually a good candidate because of the pricing alone.
  • dcroteau - Thursday, January 23, 2020 - link

    What kind of fake data is that?
    An NVMe drive at 19 degree Celsius? Less than room temperature?

    They run notoriously hot and wouldn't be below 30C in any circumstances. They can go as high as 70C without a proper heat sink.

    Even with proper cooling, they will never be below room temp. 19C is very frisky for a room temperature.
  • ganeshts - Friday, January 24, 2020 - link

    It is winter here in CA and the room temperature in my lab is around 63F (as I rarely turn on the air-conditioning in the lab for winters - the benchmarking testbeds are operated remotely / headless).
  • Meteor2 - Saturday, January 25, 2020 - link

    My heating never goes above 19C. Put a jumper on and save the planet.
  • regsEx - Thursday, January 23, 2020 - link

    USB 3.2 Gen 2 is just rebranded USB 3.1. Actual USB 3.2 is Gen 2x2.
  • Tomatotech - Friday, January 24, 2020 - link

    I hope you understood that as I didn’t at all.

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