Rapid advancements in flash technology and continued improvements in high-speed interfaces have driven the growth of small, bus-powered portable SSDs. Over the last few years, these types of drives have relied on a dual-chip solution - typically placing a SATA or NVMe SSD behind a USB bridge chip. SSD controller vendors such as Phison and Silicon Motion have recognized the growth potential in the portable SSD market and come out with USB Flash Drive (UFD) controllers employing high-speed direct-attach interfaces on the upstream side, and directly talking to the flash packages downstream. These controllers have now created a new category of portable SSDs by lowering the cost without sacrificing performance.

Kingston's DataTraveler Max was introduced in August 2021 as a USB-C flash drive capable of hitting 1GBps speeds. The claimed performance numbers justify calling the thumb drive as a portable SSD. While Kingston did not publicly disclose the internals of the drive, the form-factor and performance numbers point to the use of a native UFD controller. Kingston is not the first to the market with such a high-performance portable SSD. Crucial's X6 (updated in 2021 with Phison's U17 UFD controller) reaches speeds of 800MBps+, but it retains the industrial design of the older version (which was a SATA drive behind a USB - SATA bridge).

To that end, today we're digging into the 1TB version of the DataTraveler Max (referred to here on as DT Max), which Kingston has provided. We'll be taking a look at the performance, power efficiency, and value proposition of the DT Max. We've also cracked the drive open in order to confirm which UFD controller Kingston is using.

Introduction and Product Impressions

External bus-powered storage devices have grown both in storage capacity as well as speeds over the last decade. Thanks to rapid advancements in flash technology (including the advent of 3D NAND and NVMe) as well as faster host interfaces (such as Thunderbolt 3 and USB 3.2 Gen 2x2), we now have palm-sized flash-based storage devices capable of delivering 2GBps+ speeds.

The thumb drive form factor is attractive for multiple reasons - there is no separate cable to carry around, and the casing can be designed to include a keyring loop for portability. Vendors such as Corsair and Mushkin briefly experimented with SATA SSDs behind a USB bridge chip, but the thermal solution and size made the UFDs slightly unwieldy. While the weight was fine for a Type-A male connector, putting such drives behind a Type-C connector would have required extensive redesign. The introduction of high-performance native UFD controllers has made this category viable again.

Kingston's DT Max retains the traditional DataTraveler thumb drive form-factor. However, it takes full advantage of the USB 3.2 Gen 2 Type-C male connector by promising 1GBps speeds. Available in three capacities - 256GB, 512GB, and 1TB, Kingston says that they can deliver those high speeds across all three SKUs.

The industrial design is slightly different from other DataTraveler UFDs. The Type-C male connector is protected by a sliding cap. Retracting and covering it again can be done with a single hand. There is also a blue LED indicator and a keyring loop at the end. The thumb drive measures 82.6 mm x 22.3 mm x 9.5 mm and tips the scales at around 12.5 grams.

Tearing down the UFD is a simple matter of popping off the sliding cap and prying out the internal cover. There are no screws in the drive. The bare board inside has no special thermal solution. We see Silicon Motion's SM2320 UFD controller here, but the package seems to be different from the one we saw in the SM2320 USB 3.2 Gen 2x2 reference design reviewed earlier this month.

Kingston XS2000 (SM2320 Reference Design) [top] vs. Kingston DT Max (SM2321?) [bottom]

For comparison purposes, we have only limited 1TB results with our new test suite and testbed. Hence, we only present metrics from two USB 3.2 Gen 2 NVMe bridges from Akasa - one using ASMedia's ASM2362, and another using Realtek's RTL9210B.

CrystalDiskInfo provides a quick overview of the capabilities of the internal storage device. Since the program handles each bridge chip / controller differently, and the SM2320 is quite new, many of the entries are marked as vendor-specific, and some of the capabilities (such as the interface) are deciphered incorrectly. The temperature monitoring worked well, though.

Prior to looking at the benchmark numbers, power consumption, and thermal solution effectiveness, a description of the testbed setup and evaluation methodology is provided.

Testbed Setup and Evaluation Methodology

Direct-attached storage devices (including thumb drives) are evaluated using the Quartz Canyon NUC (essentially, the Xeon / ECC version of the Ghost Canyon NUC) configured with 2x 16GB DDR4-2667 ECC SODIMMs and a PCIe 3.0 x4 NVMe SSD - the IM2P33E8 1TB from ADATA.

The most attractive aspect of the Quartz Canyon NUC is the presence of two PCIe slots (electrically, x16 and x4) for add-in cards. In the absence of a discrete GPU - for which there is no need in a DAS testbed - both slots are available. In fact, we also added a spare SanDisk Extreme PRO M.2 NVMe SSD to the CPU direct-attached M.2 22110 slot in the baseboard in order to avoid DMI bottlenecks when evaluating Thunderbolt 3 devices. This still allows for two add-in cards operating at x8 (x16 electrical) and x4 (x4 electrical). Since the Quartz Canyon NUC doesn't have a native USB 3.2 Gen 2x2 port, Silverstone's SST-ECU06 add-in card was installed in the x4 slot. All non-Thunderbolt devices are tested using the Type-C port enabled by the SST-ECU06.

The specifications of the testbed are summarized in the table below:

The testbed hardware is only one segment of the evaluation. Over the last few years, the typical direct-attached storage workloads for memory cards have also evolved. High bit-rate 4K videos at 60fps have become quite common, and 8K videos are starting to make an appearance. Game install sizes have also grown steadily even in portable game consoles, thanks to high resolution textures and artwork. Keeping these in mind, our evaluation scheme for portable SSDs and UFDs involves multiple workloads which are described in detail in the corresponding sections.

• Synthetic workloads using CrystalDiskMark and ATTO
• Real-world access traces using PCMark 10's storage benchmark
• Custom robocopy workloads reflective of typical DAS usage
• Sequential write stress test

In the next section, we have an overview of the performance of the Kingston DT Max in these benchmarks. Prior to providing concluding remarks, we have some observations on the UFD's power consumption numbers and thermal solution also.

Performance Benchmarks

Benchmarks such as ATTO and CrystalDiskMark help provide a quick look at the performance of the direct-attached storage device. The results translate to the instantaneous performance numbers that consumers can expect for specific workloads, but do not account for changes in behavior when the unit is subject to long-term conditioning and/or thermal throttling. Yet another use of these synthetic benchmarks is the ability to gather information regarding support for specific storage device features that affect performance.

Synthetic Benchmark - ATTO

Kingston claims read and write speeds of 1000 MBps and 900 MBps respectively, and these are backed up by the ATTO benchmarks provided below - in fact, the numbers are actually higher than the claimed ones. ATTO benchmarking is restricted to a single configuration in terms of queue depth, and is only representative of a small sub-set of real-world workloads. It does allow the visualization of change in transfer rates as the I/O size changes, with optimal performance being reached around 512 KB for a queue depth of 4. The performance is slightly behind the bridge solutions in terms of raw numbers.

Full System Drive Benchmark Bandwidth (MBps)Full System Drive Benchmark Latency (us)Full System Drive Benchmark ScoreExpand All

Given the analysis of the aforementioned results, it is clear that a bridge solution delivers a better experience in most cases. However, the Kingston DT Max delivers respectable numbers equivalent to that of a DRAM-less PCIe 3.0 x2 NVMe SSD behind a USB 3.2 Gen 2 bridge.

Miscellaneous Aspects and Concluding Remarks

The performance of the Kingston DT Max in various real-world access traces as well as synthetic workloads was brought out in the previous section. We also looked at the performance consistency for these cases. Power users may also be interested in performance consistency under worst-case conditions, as well as drive power consumption. The latter is also important when used with battery powered devices such as notebooks and smartphones. Pricing is also an important aspect. We analyze each of these in detail below.

Worst-Case Performance Consistency

Flash-based storage devices tend to slow down in unpredictable ways when subject to a large number of small-sized random writes. Many benchmarks use that scheme to pre-condition devices prior to the actual testing in order to get a worst-case representative number. Fortunately, such workloads are uncommon for direct-attached storage devices, where workloads are largely sequential in nature. Use of SLC caching as well as firmware caps to prevent overheating may cause drop in write speeds when a flash-based DAS device is subject to sustained sequential writes.

Our Sequential Writes Performance Consistency Test configures the device as a raw physical disk (after deleting configured volumes). A fio workload is set up to write sequential data to the raw drive with a block size of 128K and iodepth of 32 to cover 90% of the drive capacity. The internal temperature is recorded at either end of the workload, while the instantaneous write data rate and cumulative total write data amount are recorded at 1-second intervals.

CrystalDiskMark Workloads - Power Consumption
TOP: Kingston DT Max 1TBAkasa AK-ENU3M2-03Akasa AK-ENU3M2-04 (NVMe)	BOTTOM: Akasa AK-ENU3M2-03Akasa AK-ENU3M2-04 (NVMe)Kingston DT Max 1TB

While bridge chip-based solutions operate at around 2.5W with peaks of 5W+, the Kingston DT Max is much more power efficient. The UFD goes to deep sleep of around 8 - 9mW after around 20 minutes of lack of traffic. Average power usage is around 1.4W, and the peak is only 3.04W.

Final Words

The Kingston DT Max is available for pre-order today - hovering around $166 on B&H. It appears that retailers are happy to tag on a premium to this product for its uniqueness, given that the 2GBps-capable Kingston XS2000 is priced lower at $160. Given that the 256GB and 512GB versions are priced at $58 and $97, a sub-$150 price for the 1TB Data Traveler Max would work better on the current market. The real competition here is the dual-interface Akasa AK-ENU3M2-04 with its male connectors and user-replaceable SSD. Including a 1TB SSD would still land it at a sub $140 price point.

Overall, the Kingston DataTraveler Max is a hands-down winner in terms of industrial design, form-factor, performance, power efficiency, and uniqueness. The SLC cache is big enough for users to not worry too much about the sub-100 MBps performance numbers seen for extreme workloads. That said, there is some scope for improvement in thermal design. Additionally, a dual-connector (Type-C + Type-A) product could be a great addition to the family. Given what we have seen of Silicon Motion's SM2320 in the Kingston DataTraveler Max, it is clear that USB thumb drives are approaching portable SSDs in performance - that is good from a consumer viewpoint.