Miscellaneous Aspects

The thermal design of external storage enclosures has now come into focus, as high-speed SSDs and interfaces such as USB 3.1 Gen 2 can easily drive up temperatures. This aspect is an important one, as the last thing that users want to see when copying over, say, 100 GB of data to the drive inside the enclosure, is the transfer rate going to USB 2.0 speeds. In order to identify the effectiveness with which the enclosure can take away heat from the internal drive, we instrumented our robocopy DAS benchmark suite to record various parameters while the robocopy process took place in the background. Internal temperatures can only be gathered for enclosures that support S.M.A.R.T passthrough. Readers can click on the graphs below to view the full-sized version. We see that the USB 3.1 configuration finished our benchmarks faster, and the temperature of the internal SSD topped out at 56C. The USB 3.0 case took longer, but, the temperature topped out at 54C. On the other hand, the temperature barely touched 48C when the same benchmark was run using a USB 2.0 port in our testbed.

Storage Enclosure Thermal Characteristics

It is challenging to isolate the power consumption of the storage bridge alone while treating the unit as a black box. We strive to present results in a comparative manner, but, this being the first M.2 NVMe to USB 3.1 Gen 2 enclosure, we can only compare the numbers when different interfaces (USB 3.1 / USB 3.0 / USB 2.0) are used. The numbers for the other storage bridges are only given for reference. Towards this, we processed the same workloads for each case (CrystalDiskMark 5.1.2's benchmark traces with a region size of 8GB and the number of repetitions set to 5). Plugable's USBC-TKEY power delivery sniffer was placed between the host PC and the storage bridge to record the power consumption.

Power Consumption - CrystalDiskMark

Over USB 2.0, the power peaked at 2.8W, while the unit idled at 1.1W. The numbers for the USB 3.0 and USB 3.1 cases were 3.9W / 1.2W and 5W / 1.25W respectively.

SATA - USB storage bridges that support UASP fully can translate the SCSI UNMAP command to TRIM commands for SSDs connected to the downstream port. In the case of M.2 NVMe - USB storage bridges, the bridge chip has to recognize the corresponding NVMe command and pass it downstream appropriately.

Checking for TRIM support has been a bit tricky so far. CyberShadow's trimcheck is a quick tool to get the status of TRIM support. However, it presents a couple of challenges: it sometimes returns INDETERMINATE after processing, and, in case TRIM comes back as NOT WORKING or not kicked in yet, it is not clear whether the blame lies with the OS / file system or the storage controller / bridge chip or the SSD itself. In order to get a clear idea, our TRIM check routine adopts the following strategy:

  • Format the SSD in NTFS
  • Load the trimcheck program into it and execute
  • Use the PowerShell command Optimize-Volume -DriveLetter Z -ReTrim -Verbose (assuming that the drive connected to the storage bridge is mounted with the drive letter Z)
  • Re-execute trimcheck to determine status report

Conclusions can be made based on the results from the last two steps.

As JMicron claims in their marketing material for the JMS583, the M2X enclosure using it has no trouble activating TRIM on the installed SSD.

In the introductory section, I had mentioned that it is very important to ensure that the SSD being used has an appropriate active state power profile. In order to ensure wide compatibility, the enclosure along with the SSD must stay within the minimum guaranteed USB 2.0 power delivery envelop (Update: 500mA @ 5V, corresponding to 2.5W for USB 2.0, and 900mA @ 5V, corresponding to 4.5W corresponding to USB 3.x). Now, it must be noted that the JMicron JMS583 main board, by itself, consumers around 700 mW when active. This leaves around 3.8W for the M.2 NVMe SSD. (Update: Note that this is for connection to a USB 3.x port)

The gallery above presents the active power states information for all the M.2 NVMe SSDs that I had available for testing. All of them worked well in the enclosure. However, I did find one Amazon review indicating the inability to use an Intel 600p SSD inside the M2X. Billy, our SSD reviewer, sent over the supported power states table for the Intel 600p, and it turned out that the lowest active power state was configured by the firmware to be 3.8W. Though it is likely that the SSD would never hit it when operating with a PCIe 3.0 x2 link, we believe that the JMicron bridge chip / firmware takes into account the nature of the USB host as well as the available active power states in the SSD to ensure safe and reliable operation under all possible circumstances. As it stands, as long as the SSD being installed has a sub-3.8W active power state, it should be good to use in the M2X enclosure connected to a USB 3.x port. (Update: Even with USB 2.0 ports, the enclosure with a PCIe 3.0 x2 SSD stays below 2.5W throughout except for a small spike in one of the workloads. It is possible that some legacy systems or power-constrained USB 2.0 ports could have trouble with the enclosure under some specific workloads. However, almost all users are going to be using this enclosure with a USB 3.x port, and we believe this is a minor issue compared to the internal SSD itself not supporting a suitable power state)

Closing Thoughts

Coming to the business end of the review, the M2X enclosure is priced at around $40, depending on the retailer. And while MyDigitalSSD can't claim to be the first vendor to be shipping a JMS583-based bridge – there are plenty of questionable imports available at Amazon and elsewhere – they are the first vendor with a significant North American presence to do so. Which means that, at least for the moment, they're holding the high ground in this market, helped all the more by the fact that the M2X is a complete consumer-friendly package with the appropriate screwdriver and other tools & cables required.

The end result is that MyDigitalSSD has a unique product in the North American market (for now) at the right price point. It might make sense for MyDigitalSSD to also offer a pre-built external SSD similar to the configuration we used (A DIY MyDigitalSSD SBX + M2X, which is at $256 for the 1TB version). Even at the DIY price, the configuration simply blows away the SanDisk Extreme Portable ($210) and the Samsung T5 ($228) in the performance per dollar metric while retaining the same compatibility across a wide range of host systems.

Performance Benchmarks
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  • Impulses - Thursday, November 1, 2018 - link

    Is there anything like this which would work with an M.2 AHCI but PCI-E drive? I realize that's a rarity, but I have a first gen SM951 that I'd like to use externally... Seems all the current bridges are made for SATA M.2 drives or strictly NVMe, and I'm guessing the SM951 won't play nice with either.
  • mapesdhs - Thursday, November 1, 2018 - link

    Typo I reckon...

    "... since the bottleneck fot shifted to the SSD side."

    I think you meant "got", but that's bad writing btw, just say, "... bottleneck moved to the SSD."

    And on the last page, "... consumers around 700 mW when active."

    I like the look of this device. Alas no sign of it in the UK yet.
  • Dug - Thursday, November 1, 2018 - link

    I wish someone would make a 2-4 small box for NVMe with thunderbolt and no raid controller to keep costs down.
  • PushT - Tuesday, March 12, 2019 - link

    There are two very important aspects to these enclosures imo. The thermal aspect and what the enclosure will be used for.
    I think you are skipping an important point when choosing the drive for these tests. When people use a usb device like this they usually want high reliable SUSTAINED transfer speeds. THAT is actually more important than burst speeds with crappy TLC drives. I mimicked your photo/video transfer tests with an MLC oem drive(whaaat??), and I blew the socks off your usb 3.1 gen 2 results using usb 3.1 gen 1(usb 3.0). You know why ? Because the sustained read/ write speeds of my internal & external m.2's do not depend on cache. So why use a high quality drive you say ? Because the native speed of TLC will have you throwing your adapter out the freaking window ....
    I bought a jms583 bridge pcb cheaply, without enclosure, and I would(of course!) like to use it as a memory stick. Who wouldn't ? The remaining part of the puzzle is the enclosure, because as testing and experience shows, throttling does occur.
  • PushT - Tuesday, March 12, 2019 - link

    Just to be clear, when talking about sustained transfer rates in these kind of situations, I don't mean 10 GB. My trials were done with 100+ GB's , at which point you would return to native speeds of TLC, while I would retain high speeds. To put it into perspective( and I have already tried several m.2 enclosures with both sata and name); It's no good to me if your "testing" reveals that I could potentially get a burst speed of 1TB at some point during the file transfer e.g. I think most people actually would be content with "Sata speed", as long as that speed is sustained through the transfer. ~550 MB/s sustained, I would take that all day over burst speed for 30 seconds + 15-20 minutes for the rest of the file transfer.
  • PushT - Tuesday, March 12, 2019 - link

    I am sorry to post multiple times here, but I do not want people to be mislead. Please read the page that I link to here, it is indeed a review done by anandtech, and it shows by numbers essentially how putting a 2-lane, low-end TLC drive into your DIY enclosure will leave you disappointed when in real life use. A sustained 349/256 MB/s read/write sequential speed would not even satisfy you on a sata bridge, so choose wisely when picking your m.2 drive. My suggestion would definitely be an mlc oem drive.
  • PushT - Tuesday, March 12, 2019 - link

  • Sailor23M - Tuesday, October 1, 2019 - link

    Thanks for the heads up, I just bought one of these and looking to pair it with a drive.
  • PushT - Wednesday, March 20, 2019 - link

    Haha... That was a good one I must admit. Rather than 1TB I would have like to have written 1GB/s.

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