A lot of attention has been paid to high-speed I/O interfaces for computing systems over the last five years. Flash-based storage media capable of multi-Gbps throughput have become very affordable. Display resolutions have also seen a rapid rate of increase. The necessity to support multiple such devices in both consumer and professional computing solutions have exposed the limitations of the traditional external I/O interfaces. While USB 3.x has become successful as an interface for high-speed peripherals, it does not handle display output. Intel has been attempting to solve this problem with Thunderbolt Technology since 2011. Unfortunately, the uptake outside the Apple ecosystem for the first two versions has been minimal at best. Thunderbolt 3, however, promises to be a game-changer. Systems and motherboards with Thunderbolt 3 support started shipping in late 2015. The first Thunderbolt 3 peripheral to appear in the market was the Akitio Thunder3 Duo Pro, a hardware RAID solution with two drive slots. This review looks at the various features of Thunderbolt 3 and what the Akitio Thunder3 Duo Pro brings to the table.

Introduction and Setup Impressions

Direct Attached Storage (DAS) units have been the go-to devices for consumers looking to store and have fast access to large amounts of data. The advent of high-speed interfaces such as USB 3.x and Thunderbolt have enabled a new generation of DAS units that allow the host system to access the member disks without any bottlenecks. We have looked at a few DAS solutions with Thunderbolt 2 before. Today, we are reviewing the first storage solution with Thunderbolt 3, the Akitio Thunder3 Duo Pro. The unit has daisy chaining support (i.e, two Thunderbolt 3 ports), a USB 3.1 Gen 1 device interface and a full-sized DisplayPort 1.2 output that is driven by the DisplayPort lanes in the Thunderbolt 3 link.

The Akitio Thunder3 Duo Pro is meant for desktop use and needs an external 90W power adapter (12V @ 7.5A). The chassis design also allows for stacking, if needed. In addition to the main unit and the power adapter / cord, the package also includes a Thunderbolt 3 cable (capable of 40Gbps data transfer) and a USB 3.1 Gen 1 Type-B male to Type-A cable. 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.

Akitio Thunder3 Duo Pro Specifications
Internal Storage Media 2x 2.5" / 3.5" Drives
Interface 2x Thunderbolt 3 + 1x USB 3.1 Gen 1
RAID Modes RAID 0 / RAID 1 / JBOD / SPAN - Hardware Selection Dial
Cooling Aluminium Chassis + Fan
Power Supply 100-240V AC Switching Adapter (12V @ 7.5A DC)
Dimensions 23.8cm x 14.3cm x 9.4cm
Product Page Akitio Thunder3 Duo Pro
Price $378

The gallery below takes us around the aluminum chassis. Important aspects to note include indicator LEDs for the two drives in the front panel and the perforations (which have a filter on the inside) that allow air to be pulled into the unit, over the drives and out through the fan. The rear panel is flanked on either side by screws that can be removed without the need for any tools. Loosening them allows for the external chassis to slide out.
The rear panel has a fan and a switch to control it (can be turned off for SSDs). Two Thunderbolt 3 ports, a full-sized DisplayPort 1.2 output, a power input jack and a USB 3.1 Gen 1 Type-B female port make up the lower part of the rear panel. A Kensington lock slot and the RAID-level selection indicator form the rest of the features.

The RAID-level selection indicator is covered by a plastic film from the inside that makes it impossible to accidentally change the RAID level without opening up the unit.  The gallery below shows the internal components of the Akitio Thunder3 Duo Pro.

On the board side of things, we have the Intel Alpine Ridge Thunderbolt 3 controller in its dual-port form (). The ASMedia ASM1153E fulfills the SATA to USB bridge functionality for the USB 3.1 Gen 1 device port. On the SATA backplane, we have the ASMedia ASM1062R SATA RAID controller that bridges 2x SATA III ports to two lanes of PCIe 2.0. The backplane also has an ASMedia ASM1456 signal switch to mux / demux SATA signals.

The setup process is simple, since the Thunder3 Duo Pro involves hardware RAID. Installing the SSDs or HDDs is a simple tool-less affair. Removal is a bit complicated, since the drives have to be gently tugged out from the SATA connector. A flat screwdriver can be used to set the desired RAID level (RAID0, RAID1, JBOD or SPAN). In case of a live switch of RAID level (i.e, change while the unit is powered on, it is necessary to press the 'Set RAID' button that is visible in the rear panel once the chassis has been slid off. Otherwise, one just needs to set the pointer to the desired RAID level and boot up the unit.

In the rest of the review, we first take a look at Thunderbolt 3 in detail, followed by a description of how our testbed was built and details of our evaluation methodology for the unit. We then talk about the various standard performance benchmarks. Following that, some special Thunderbolt-only aspects such as daisy chaining and its performance implications are discussed.

The Nuts and Bolts of Thunderbolt 3
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  • DanNeely - Thursday, April 14, 2016 - link

    Were there any issues with video quality/reliability in your daisy chaining test?

    I'm guessing not since you didn't come close to saturating the bus in this test, but I'd be really interested in seeing what happens if you ever get to play with something like a 10bay SSD enclosure and external GPU that could devour most of the bandwidth for what ever they're running.
  • ganeshts - Thursday, April 14, 2016 - link

    The DisplayPort lanes are muxed together with the PCIe lanes, and, if any throttling were to happen, it would be on the PCIe lanes, and not the DisplayPort ones.

    But, yes, we were way short of saturating the link because we were not equipped properly to test that aspect.
  • DanNeely - Thursday, April 14, 2016 - link

    Ok. I didn't know the DP lanes were given explicit preference in the MUXing; but I suppose that in general it's probably the right way to go.
  • repoman27 - Thursday, April 14, 2016 - link

    I just wanted to clarify that Thunderbolt supports multiple signaling modes over a single port via hardware muxing, however, when operating in Thunderbolt signaling mode, it uses protocol converters and crossbar switches to mux at the packet level. So the Thunderbolt mode is more like iSCSI or other technologies that encapsulate and transport data streams over IP networks alongside other packets. The encapsulation that Thunderbolt performs is incredibly lightweight, though, and Intel even refers to it as a "meta protocol".

    Thunderbolt seems to have fairly solid mechanisms in place for guaranteeing timely delivery of packets that are part of isochronous data streams such as DisplayPort. OG Thunderbolt did have some issues with USB audio adapters, as it had no way of knowing that the PCIe packets destined for the USB host controller in the device were particularly time sensitive.

    Bear in mind that the signaling rate of a Thunderbolt PHY is considerably higher than the versions of PCIe or DisplayPort that it's carrying. Also, it can strip out all the bit-stuffing that is normally used to maintain a constant DisplayPort data rate and just send the packets carrying actual data. Or it can essentially bit-stuff with PCIe packets instead.

    And one last niggle, Thunderbolt cables are really nothing like regular DisplayPort cables aside from sharing the miniDP connector. They're active and have four full-duplex signaling lanes, whereas DP cables are generally passive and only support half-duplex lanes for the main link.
  • DanNeely - Friday, April 15, 2016 - link

    You say USB Audio was a problem with the original generation, does that mean it's not a problem in the 2nd/3rd generation? If so, how was it fixed: Throwing more bandwidth at the problem, or by doing usb packet inspection to ID and prioritize the usb audio stream?

    Also, am I right in assuming a TB dock with audio out would be using a built in usb audio device?
  • repoman27 - Saturday, April 16, 2016 - link

    Here's Anand's description of the original problem: http://www.anandtech.com/show/4832/the-apple-thund...

    Honestly, I have no idea if the issue with the Promise Pegasus R6 drives (one of the very first Thunderbolt devices to make it to market) was ever fully resolved. In the meantime, Apple has released updates to their EFI, Thunderbolt host, device and cable firmware (yup, even the cables have firmware), and USB host controller and audio device drivers. If I had to guess, making the USB host controller / audio device drivers Thunderbolt aware and capable of isochronous bandwidth reservation (a la FireWire) might have solved the problem. However, Anand's conclusions about the root cause are different than mine, so I could be way off base.

    And yes, AFAIK Thunderbolt docks all use USB devices in some form or another for audio I/O.
  • danbob999 - Thursday, April 14, 2016 - link

    "the street price of $378 sounds reasonable"

    Sorry but no, a hard drive case is not worth $378. Wake me up when it cost less than $30.
  • NCM - Thursday, April 14, 2016 - link

    On the off chance that you're just ignorant, not a troll, I'll point out that it's not a "hard drive case." This enclosure holds two drives, it provides a selection of hardware RAID options, and it has very high speed connectivity via Thunderbolt 3. It's also one of the first products of of it kind. Each one of those things adds cost.

    Yes it's not cheap, but this kind of product will become less expensive over time. For comparison purposes we have a bunch of 2.5" drive RAID enclosures at the office that run about $270 each (empty), see http://www.bhphotovideo.com/c/product/882789-REG/C...
  • danbob999 - Thursday, April 14, 2016 - link

    This is a 2x3.5" case. It's too bulky to be useful for 2.5" SSDs. It's too expensive and no faster and a plain USB3 case when you put two 3.5" HDDs.
    I wasn't trolling, I seriously don't see any use case for it. The fact that it needs a fan to operate just make it worse.
  • Guspaz - Thursday, April 14, 2016 - link

    Can you point out a 2x3.5" USB 3 hard drive enclosure with hardware RAID support for under $30? I get that you think $378 is too much, but $30 seems far more unreasonable a price than $378.

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