Bridging Solution Springs A Surprise

SK hynix is one of the few vertically integrated manufacturers in the flash-based storage market (along with Samsung, Micron / Crucial, Western Digital, and Kioxia). The company is well-established in the OEM market. A few years back, they also started exploring direct end-user products. Internal SSDs (starting with the Gold S31 and Gold P31) were the first out of the door. Late last year, the company introduced the Beetle X31 portable SSD, its first direct-attached storage product. In February, a complementary product was introduced - the Tube T31 Stick SSD.

The Beetle X31 is a portable SSD with a Type-C upstream port and a separate cable. The Tube T31 is a take on the traditional thumb drive with a male Type-A interface. The size of the Beetle X31 makes the use of a bridge solution obvious. Our investigation into the Tube T31 also revealed the use of the same internal SSD, albeit with a different bridge. This review takes a detailed look at the Tube T31, including an analysis of its internals and evaluation of its performance consistency, power consumption, and thermal profile.

Introduction and Product Impressions

USB flash drives have grown both in storage capacity and speeds over the last few years. Thanks to the advent of 3D NAND and rapid iterations with performance improvements in the USB specifications, we are now seeing 'stick SSDs' capable of delivering 1GBps+ speeds. This market segment has slowly been gaining members since the introduction of the Kingston's DataTraveler Max in late 2021. Some stick SSD vendors have attempted to differentiate themselves by even offering 2TB SKUs.

The high-performance 'stick SSD' segment is relatively new, and has been dominated by native UFD controllers (Silicon Motion's SM2320 in products such as the Kingston DataTraveler Max A and Transcend ESD310C, and the Phison U17 in the OWC Envoy Pro Mini for example). This is in contrast to early high-performance UFDs such as the Corsair Voyager GTX and the Mushkin Ventura Ultra which employed a SATA SSD controller behind a USB 3.0 bridge. In high-performance scenarios, the bridge solution is usually avoided for UFDs due to thermal constraints. BOM cost is also another important aspect, as UFDs usually tend / need to be priced lower than portable SSDs. Factors such as the absence of a separate cable help with that, but a bridge solution in the PCB could potentially offset the savings.

The Beetle X31 from SK hynix was a traditional portable SSD that employed a SK hynix BC711 M.2 2242 NVMe SSD behind an ASMedia ASM2362 USB 3.2 Gen 2 bridge chip. Unlike other PSSD families with a wide range of capacity options, the Beetle X31 was introduced with only two capacity options - 512GB and 1TB. The reason ended up being the single-chip BC711 internal SSD - the package integrates the flash dies, SSD controller, and DRAM for the flash translation layer as well. The highly integrated nature of the BC711 ended up limiting the number of NAND dies, and hence the limited capacity options.

The Tube T31 being reviewed today also comes in the same two capacity points - 512GB and 1TB, pointing to the likely use of the same internal SSD. The integration of the flash dies and the controller in a single package alleviates some of the BOM concerns, and a bridge-based solution based on the BC711 ends up with a similar PCB area to a native UFD controller-based solution.

The Tube T31 is relatively bulky for a USB flash drive, and is bound to interfere with devices / cables connected to neighboring USB ports. However, the dimensions are unavoidable due to the use of a M.2 2242 internal SSD and its associated thermal solution. Since this is a UFD solution, the packaging is spartan - just the user manual and the main unit in an environment-friendly recyclable box.

The clamshell case design is easily disassembled by pushing in the plastic tabs holding both sides to enable one of them to pop up and slide off. The circuit boards are shielded by a metal cladding that is held together with the aid of three screws, and further affixed to the boards with thermal pads - one on top of the bridge chip in the main board, and the other across the NVMe SSD daughterboard.

The internal SSD is a single-sided board, with a thin thermal pad on the underside used to keep it glued to the main board.

The single chip on the SSD carries the 'SK hynix HNB001T14M' package marking - which is the same as the one in the BC711 M.2 2230 / 2242 OEM NVMe SSD. This uses SK hynix's 128L V6 NAND, and integrates their in-house controller as well as DRAM.

Unlike the ASMedia ASM2362 used in the Beetle X31, SK hynix has opted for JMicron's JMS583 in the Tube T31. The JMicron solution has been around for more than 5 years now, and is currently on A3 silicon (fourth iteration of the same design with silicon bug fixes) to improve and resolve system incompatibility issues. This bridge seems to have had a recent resurgence in the market, evidenced by its use in the Silicon Power PX10 released earlier this year.

The bridge allows S.M.A.R.T passthrough, as shown in the CrystalDiskInfo screenshot below. TRIM is also available, even though it doesn't find an explicit mention.

S.M.A.R.T Passthrough - CrystalDiskInfo

The table below presents a comparative view of the specifications of the different storage bridges presented in this review.

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 SK hynix Tube T31 in these benchmarks. Prior to providing concluding remarks, we have some observations on the stick SSD's power consumption numbers and thermal solution also.

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