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


View All Comments

  • bill44 - Saturday, April 16, 2016 - link

    Agreed. If performance is what you seek, this maybe it;
  • philipma1957 - Saturday, April 16, 2016 - link

    I am more of a Mac guy then a Windows or a linux guy.
    I own 3 macs
    I own 3 windows pcs
    I own a linux pc

    Thunderbolt is all over my home and I use it for a lot of IT work on Macs.
    A portable 2 drive piece of gear like this allows for rescue work.
    Simply have a ssd in one slot with a mac os and a blank ssd 2tb samsung. go to a clients place
    boot with it and then clone and rescue the dead mac's hhd on the big ssd in your other slot.

    I do this now with an older version of thunderbolt then this one. Works great.
    I have owned a dozen thunderbolt devices and they are day and nigh over most usb3 devices in terms of being a reliable stable external booter. None of this matters to most none mac users.

    One of the great features is I can plug in a thunderbolt mac os and boot most macs.

    Windows never really allowed this. So to complain about a system like thunderbolt costing too much is okay but the truth is when you realize what thunderbolt 1 and thunderbolt 2 can do to and with someone else's mac you would say that it is too cheap .
  • LuxZg - Sunday, April 17, 2016 - link

    Is it just me or did you really comparr a performance of USB 3.1 Gen.2 SSD connected directly to PC's GEN2 port, vs it connecting to GEN1 port of a DAS and claimed that performance drop is purely due to DAISY CHAINING? Reply
  • ganeshts - Sunday, April 17, 2016 - link


    The USB 3.1 Gen 2 SSD is first connected to a PC's Gen 2 port.

    In the second case, it is connected to the Thunderbolt 3 port of the second DAS unit. Note that Thunderbolt 3 can support both Thunderbolt peripherals as well as USB 3.1 Gen 2 devices for daisy chaining. Only obvious restriction is that USB 3.1 Gen 2 devices can appear only at the end of the daisy chain.

    Also, please read specifications carefully for the USB 3.1 Gen 1 port of the DAS - The Gen 1 port is a device port - i.e, it can connect to a PC directly. It can't connect to another device like the Extreme 900 Portable SSD.
  • Zizy - Monday, April 18, 2016 - link

    1.) Could you please add USB 3.1 results for direct-attached? (just use USB cable instead of thunderbolt). Presumably the same, right? So, what is the point of Thunderbolt here? Daisy chaining?
    2.) Temperature is steadily increasing in your test. 10 minutes is quite short-ish test. What is the steady-state temperature and does it throttle at that temperature?
  • ganeshts - Monday, April 18, 2016 - link

    (1) The USB 3.1 port is USB 3.1 Gen 1 - Maximum possible bandwidth on that is theoretically 5 Gbps, but, in practice, for RAID-0 SSDs, one would get around 450 - 500 MBps. So, it will not be the same as that of Thunderbolt 3 - where we could get around 800 MBps

    (2) Temperature for SSD configuration was with the fans completely turned off. You can see that the fan 'on' case for HDDs shows that even after more than 250GB of continuous data transfer, the temperature of the HDDs is within 5C of the temperature prior to the start of the transfers. I don't expect throttling to be a concern. If it is (depending on the SSD or HDD in use), one should just turn on the fan.
  • Haravikk - Tuesday, April 19, 2016 - link

    Pretty underwhelming for the enormous price; USB3 is fast enough to handle three or even four drives if there's hardware RAID on the other end, so Thunderbolt only really offers an improvement if you're handling a JBOD enclosure, and even then two drives won't really justify it.

    Also, for the price, why aren't these hot-swap bays? Someone wanting to use paired drives in a mirror setup would benefit from being able to hot-swap in a replacement, and for the money you're spending I'd think that pretty reasonable.

    Lastly, couldn't this be bus-powered? Even 3.5" drives shouldn't require so much power the bus can't handle it, plus any good RAID controller should be able to spin them up separately (so you're not drawing peak power for both drives simultaneously).

    I dunno, I get that Thunderbolt is still a premium product, but it still feels as though the actual quality of design and features you're getting is severely lacking. Besides, being the first Thunderbolt 3 enclosure for two SATA III drives is meaningless as even Thunderbolt 1 is more than fast enough for that. Even the bigger "high end" enclosures are surprisingly poorly made and thought out for the amount of money you need to drop on them; a networked iSCSI device using ZFS with l2ARC will meet most needs, and the NAS/SAS options are just way better.
  • Questor - Tuesday, April 19, 2016 - link

    I believe computing and related has come to a point where it needs an official organization to manage and assign acronyms. Reply
  • Chad - Tuesday, April 19, 2016 - link

    As a thunderbolt user, there are several other benefits (especially for Mac's) that is brings to the table. For example, I added an external HDD, then added 5 more, 1 by 1 as time went on and as needed, for a total of 6, but only using the 1 port. On Mac's, ports are a valuable commodity. On this same iMac, I only had a few USB ports and they were quickly used up for various things. So that left the thunderbolt port... but i was able to connect 5 devices on it. None of them came even remotely close to using it's bandwidth, but for me, it wasn't about that, or about speed... but expandability. That is something worth noting, for sure. Granted, in PC land, this isn't really a concern, but on Mac's, it's a huge thing. There's also an aesthetic factor to daisey chaining, over a spiderweb hub solution. Reply
  • Haravikk - Wednesday, April 20, 2016 - link

    True, but my main point was that you're paying a pretty big premium for the Thunderbolt aspect of this device, for what is overall a pretty poor product; two 3.5" bays, not really setup well for 2.5" drives, not hot-swappable, not actually all that compact. Even little things haven't been thought through, like the place of the Thunderbolt ports under the fan, limiting you to a smaller fan size (bigger is always better when it comes to noise after all).

    Also, technically it's possible to create daisy-chained USB devices too (each one would integrate a three port hub, with one port for whatever it actually does), the only difference with Thunderbolt really is that it's a crucial part of the design so manufacturers are forced to enable chaining, whereas USB device manufacturers are happier cutting their costs and forcing us to rely on hubs.

    Also, if I've understood you right and you've got six HDDs, I'd seriously consider an 8-bay NAS instead. If you're fine with command line stuff then you can set that up with ZFS backed iSCSI, format the iSCSI volume as ZFS on your mac and assign it a chunk of your internal drive as a cache, and it's just better overall (if a little complex to setup in the first place). If someone manufactured a Thunderbolt cache device that I could plug straight between a Mac and a NAS then that would be the perfect option, but until then it's big local cache plus NAS with tons of drives for me =)

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