Feature image: Funny these days how fast a MultiDock 10G fills up. Photo credit: David Leitner
When Blackmagic Design introduced the original MultiDock at NAB 2013 — a compact, rackmount chassis with four open slots to insert 2.5-inch SATA drives like little cassettes — I thought of it as a clever novelty, nothing I could ever actually need. I had just invested in a desktop dock with a “blazing” USB 3.0 connection, to accommodate two 3.5-inch 7200 rpm SATA drives, and was still getting used to working with “bare” hard drives. Those littler 2.5-inch spinning drives that mounted in MultiDock were cute, but they were slower, the stuff of laptops, while 2.5-inch solid-state SSDs were out-of-reach and crazy-expensive.
2013 also happened to be Thunderbolt’s breakout year. The second key feature of the original MultiDock was a pair of Thunderbolt ports at the rear, the speed of which left my USB 3.0 in the dust.
What’s more, at the very same NAB 2013 where BMD introduced MultiDock, Intel announced Thunderbolt 2, which doubled Thunderbolt’s throughput by merging the original two 10 Gbps bidirectional channels into a single 20 Gbps channel. Then later that year Apple introduced the trashcan Mac Pro with its six Thunderbolt 2 ports. By NAB 2014, MultiDock had acquired Thunderbolt 2 too, as well as a new name, MultiDock 2.
Everything Changes as SSDs Rule
Five years after the debut of MultiDock 2, I live and work in a world of 2.5-inch SSDs. I routinely record 4K RAW files to the eight SSDs I use as media for my Convergent Design Odyssey 7Q+ monitor/recorder. With Blackmagic Design’s DaVinci Resolve I edit and grade using additional sets of SSDs in a fast RAID 0 configuration. The only spinning disks I buy these days are lumbering 5400 rpm large-volume drives for near-term archival storage. In other words, my world has more than caught up with Blackmagic Design’s prescient MultiDock concept.
But time and technology refuse to stand still, and while SSDs continue to evolve and conquer, Thunderbolt 2 is no longer leading-edge. That would instead be any I/O standard over the smaller, reversible, versatile USB Type-C connector, including USB 3.1 (“up to” 10 Gbps), DisplayPort and Thunderbolt 3 itself (40 Gbps, if cable is under 19 inches, 20 Gbps if longer). What makes this multi-standard hat trick possible is a unique “Alternative Mode” design spec that enables USB Type-C connectors and cables to send non-USB data. That’s why Apple’s redesigned 2016 15” MacBook Pro arrived with four tiny USB Type-C connectors only — no familiar USB Type-A, Thunderbolt, DisplayPort, HDMI, or separate power ports. One type of port for everything, a truly universal connector, small, cheap, and inevitably ubiquitous.
This year at NAB, Blackmagic Design joined the USB Type-C bandwagon with its announcement of a MultiDock 2 successor: MultiDock 10G. That pair of Thunderbolt 2 ports in the back? They’ve been replaced by a pair of USB Type-C ports hosting USB 3.1 at 10 Gbps — hence “10G.”
Like previous models, the compact MultiDock 10G is 1RU (one rack unit) high, a mere six inches deep, and rests comfortably on any surface if not rack-mounted. It is silent — no fan — and runs cool, powered by a standard IEC power cable. It is truly plug-and-play, no software or additional drivers required. (Won’t be made obsolete by future OS upgrades.) Each of four SSD ports is circumscribed by a thin rectangle that flickers deep red when its drive is accessed for data. In fact, only two attributes distinguish MultiDock 10G from its predecessors. It is now black in color instead of gray, and there are two USB-Type C ports at the rear instead of Thunderbolt 2 ports. That’s it.
Actual Rates Vary
But wait a minute, isn’t Thunderbolt 2 at 20 Gbps twice as fast as USB-C at 10 Gbps? Yes, on paper this would be the case. But in the real world there are many contingencies. Regardless of how intrinsically fast an SSD or flash drive may be, the drive’s SATA 3.0 interface will limit read/write speeds to 6 Gbps or 750 MBs (multiply Gbps x 125 to get MBs). And that’s on a good day, so to speak. Note the “up to” that precedes the “maximum” data transfer rate spec indicated for these protocols.
Anyone who has ever utilized Blackmagic Design’s Disk Speed Test (free download in the Mac app store!) to monitor the read and write speeds of their drives knows that both rates can be shifting targets. General health of the drive? Buffer size? Burst vs. continuous? How full is the drive? Are all sectors good? How capable is the built-in controller or management hardware?
According to Blackmagic Design, MultiDock 10G incorporates an independent disk interface chip into each SSD slot to mitigate SATA 3.0 bandwidth limitations. That’s potent: At the rear of MultiDock 10G is a switch that gives you a choice of ganging all four slots together into a single USB 3.1 10 Gbps channel, for which you would need only one USB Type-C cable, or sending two slots over one USB 3.1 10 Gbps channel, and the other two slots over a second 10 Gbps channel, for which you would need two USB Type-C cables.
In the latter case, you might join two SSDs into a faster RAID 0 (as I do) that approaches the 10 Gpbs USB 3.1 limit; or, as an alternative, you might elect to share MultiDock 10G between two computers, with two slots per customer — something Thunderbolt can’t do. Indeed, with the option of two independent 10 Gbps USB 3.1 channels, MultiDock 10G matches the theoretical 20 Gbps throughput of MultiDock 2’s Thunderbolt 2, which, as explained above, delivers but one channel only.
Examining the performance of a Western Digital 1TB SSD by means of Blackmagic Design’s Disk Speed Test, I got read/write continuous speeds of 450/510 MBs from MultiDock 10G over USB 3.1, compared to 345/380 MBs from MultiDock 2 over Thunderbolt 2. That’s an impressive bump!
Testing a two-disk RAID 0 of Samsung SSDs, I clocked 870/680 MBs from MultiDock 10G compared to 650/725 MBs from MultiDock 2. Faster read, slower write, all blazingly fast. As I said, contingencies — and of course YMMV (your mileage may vary).
The bottom line is that USB 3.1 can compare favorably to Thunderbolt. Who would have thought this a few years ago?
Unlike Thunderbolt, which requires expensive cables with active electronics, USB 3.1 allows for cheaper cables using simple USB Type-C connectors. The trade-off is that USB 3.1 over USB Type-C cables can’t enable daisy-chaining like Thunderbolt. But perhaps that is a small price to pay, given the growing universality of USB Type-C. Thunderbolt was an Intel innovation famously embraced first by Apple. It is cross-platform but has never extensively caught on with consumers, partly because of those expensive cables. Blackmagic strives to be agnostic — its software typically runs on Mac OS, Windows, and Linux — and the broad adoption of USB Type-C would seem to better suit their long-term goals.
A final note on USB-C cables: they’re not created equal! They may look the same on the outside, but on the inside it’s a different story. The disk speed tests I described above were conducted using a 1-meter USB-IF Certified 10 Gbps Gen 2 USB C-to-USB C cable made by the company Cable Matters. (USB-IF is the USB Implementers Forum, a not-for-profit that promotes USB standards and compliance.) I also ran these tests using the white 2-meter USB C-to-USB C cable that came with my MacBook Pro for charging. At B&H the specs say this cable can achieve “up to 480 Mbs Data Transfer Rate,” but when I ran tests on both the 1TB SSD and two-SSD RAID 0, in both cases this cable barely managed read/write speeds of 40 MBs, which is pathetic.
Unfortunately USB Type-C cables are all physically identical, and there is no way by mere inspection to tell what’s on the inside, or what tasks they were optimized for. (Color-coding would be nice someday.) Wirecutter recently tested and compared a good number of USB Type-C cables here. Needless to say, to get the most from your zippy MultiDock 10G, you’ll want a USB Type-C cable that sings.
Author: D.W. Leitner
David Walker Leitner is a producer, cinematographer, and DP on television, feature-length documentaries and feature films. A former I.A.T.S.E. 644 Director of Photography, Leitner has photographed for documentary directors Fred Wiseman, Allan Miller, Alan Berliner, Joe Berlinger, DeWitt Sage, Oren Rudavsky, and Doug Block among others. He has key credits in over forty feature-length documentaries filmed in the UK, South & Central America, East & West Europe and former Soviet Union, including as director/producer/DP.
As Director of New Technology at Du Art Film Laboratory in the 1980s, he produced innovations in 16-to-35mm blow-ups, film camera lens testing, film timecode, and film-to-tape transfers. In 2018, David was named a SMPTE Fellow to acknowledge his work as both an executive and an engineer in the media industry.