The benefits of Thunderbolt 3 and its 40 Gbps link are best realized in a daisy-chain configuration involving multiple high-bandwidth I/O peripherals. The Alpine Ridge Thunderbolt 3 controller in a host connects to the CPU using a PCIe 3.0 x4 link. From the perspective of a single device that is not a huge drive array, it is likely that a PCIe 3.0 x4 SSD is best suited to fully utilize the available bandwidth. AKiTiO recently started selling their Thunder3 PCIe SSD. It puts a 1.2TB Intel SSD 750 PCIe 3.0 x4 NVMe add-in card in a standard two-port Thunderbolt 3 aluminum chassis along with a dedicated DisplayPort output.

Introduction and Setup Impressions

AKiTiO is one of the first vendors to come out with Thunderbolt 3 peripherals. We have already reviewed their first offering - the Thunder3 Duo Pro 2-bay DAS. It turned out to be a great introduction to the Thunderbolt 3 peripheral market (especially considering that it was the first one out of the door). A 2-bay DAS was never going to make the Thunderbolt 3 controller sweat, even with a couple of SATA SSDs in it. AKiTiO's second Thunderbolt 3 product, the Thunder3 PCIe SSD, goes all out in search of the performance crown.

The Thunder3 PCIe SSD is meant for desktop use and needs an external 72W power adapter (12V @ 6A). In addition to the main unit and the power adapter / cord, the package also includes a Thunderbolt 3 cable (capable of 40Gbps data transfer). A cable-tie, quick setup guide, warranty terms and a reminder to update to the latest drivers / firmware for the host PC are also included. The detailed specifications of the unit are provided in the table below.

The gallery below takes us around the aluminum chassis and the internals. There is a LED indicator in the front panel to indicate power / access status (doesn't light up unless both the power adapter and Thunderbolt link are active). There are perforations in the front panel, and a fan directly behind it. The opening mechanism is similar to the Thunder3 Duo Pro - loosening the two tool-less screws in the back panel allows the chassis to slide out. It is possible to replace the fan, if needed. However, the installed PCIe SSD (add-in card) can't be taken out without voiding the warranty.

The main board seems to be based on the inXtron Thunderbolt 3 Hardware Development Kit. The board also contains Alpine Ridge in its dual-port form (Intel DSL6540).

Unlike the Thunder3 Duo Pro, the setup process is plug-and-play. There are no RAID buttons on the unit. However, it is necessary to install the Intel NVMe drivers in order to get the best performance out of the product. The Intel SSD Toolbox also allows users to monitor the health of the SSD 750 inside the Thunder3 PCIe SSD.

Hardware Analysis

A bus-powered enclosure would have been nice, but AKiTiO has opted to go for a more versatile solution with a dual-port design. The second port can also be used to connect another Thunderbolt 3 or USB 3.1 Gen 2 or any other Type-C peripheral. That device can sink power too - which leaves no option for AKiTiO. An external power adapter is definitely needed.

The Intel SSD 750 inside the enclosure is visible as a physical disk on the host. SMART attributes can be tracked, and, for all practical purposes, the SSD 750 is a PCIe 3.0 x4 NVMe drive connected to the host.

The specifications of the Intel SSD 750 1.2TB drive in the Thunder3 PCIe SSD are summarized in the table below.

Direct-Attached Storage Performance

The Thunder3 PCIe SSD was formatted in exFAT before being subject to our benchmarking routine. In order to evaluate the DAS aspect of the unit, we utilized the testbed outlined in the table below to test the performance.

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. The other usage scenario (particularly for multimedia-editing professionals that are the target market for the Thunder3 PCIe SSD) is importing files directly off the DAS into a multimedia editing program such as Adobe Photoshop. Prior to taking a look at the real-life benchmarks, we first check what ATTO and CrystalDiskMark have to report for the Thunder3 PCIe SSD. We see numbers around 2500 MBps for sequential transfers, correlating well with AKiTiO's performance claims.

In order to tackle the first real-life use-case, we created three test 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)

For the second use-case, we take advantage of PC Mark 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 graphs. Note that the bandwidth number reported in the results don't involve idle time compression.

Some context to the above numbers can be gathered from our last DAS review with the benchmark numbers presented using graphs. Given that the PCIe SSD simply leaves those USB drives in the dust, and the fact that the interface is different, we decided it would not be an apples-to-apples comparison if the numbers were to be presented / compared in the same set of graphs.

We have already talked about the Thunderbolt software and how it provides more security compared to connecting traditional USB peripherals. Detailed coverage of the Intel SSD Toolbox is also beyond the scope of this review. However, there are a couple of aspects - performance consistency and power consumption - that bear relevance in the day-to-day usage of the Thunder3 PCIe SSD.

Performance Consistency

Our performance consistency test takes the robocopy benchmark described in the previous section and instruments it to record the drive temperature as well as instantaneous transfer rates during the process.

The active thermal solution helps a lot, with the SSD barely going above 33C in the course of transferring more than 250GB of data continuously. There is absolutely no thermal throttling at play in the Thunder3 PCIe SSD, and we don't expect any workload to be really able to stress the fan-based cooling mechanism much.

Power Consumption

The power consumption of the Thunder3 PCIe SSD was recorded at the wall while processing the CrystalDiskMark benchmark, as well as over the course of processing our DAS test suite (including PCMark 8 storage bench).

The above graphs show that the PCIe SSD itself can consume upwards of 16W for certain workloads. The unit idles at around 7W. Utilizing the DisplayPort output and/or adding another device in a daisy-chain configuration is also bound to drive up these numbers (particularly if the added device is bus-powered).

Final Words

The strength of the Intel SSD 750 lies in performance consistency with random I/O intensive workloads. This is not something evident in the typical DAS workload. That said, the SSD 750 has the highest possible capacity of any consumer drive model that uses a PCIe 3.0 x4 NVMe interface. Considering the target market, it makes sense that AKiTiO uses the highest capacity model in the only version of the Thunder3 PCIe SSD. On the other hand, a bus-powered enclosure using a M.2 SSD with a better guaranteed endurance rating (in terms of drive writes per day (DWPD)) would be nice, though such a product would probably target a different use-case.

Coming to the business end of the review, it can definitely be said that the Thunder3 PCIe SSD is a unique product - It is the only product we are aware of that can put the Intel SSD 750 to use in a direct-attach scenario. The key here is that the storage is not tied to a single computer, and a portability option is available. Such fast and massive storage is a boon for multimedia editors working as a team, or, across multiple locations.

The pricing aspect is a bit shocking at first - $1300 for 1.2TB is more than $1/GB (the last Thunderbolt SSD that we evaluated - the LaCie Rugged Thunderbolt - was priced at $1/GB, but limited to SATA speeds). However, one must note that the Intel SSD 750 1.2TB add-in card itself still retails between $1018 and $1150. The Thunderbolt 3 enclosure with daisy-chaining capabilities and a dedicated DisplayPort output adds comparatively little to the final cost of the Thunder3 PCIe SSD. Considered standalone, the Thunder3 PCIe SSD is an technically exciting product that will also draw the attention of professional users. We would like to see AKiTiO add a bus-powered PCIe SSD to round out their Thunderbolt 3 Series.