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LaCie 2Big 20TB Thunderbolt 3 Storage Dock

MPG tested the about $1199 LaCie 2Big 20TB. The LaCie 2Big is available in 8/12/16/20TB capacities.

LaCie 2Big 20TB Thunderbolt 3

The LaCie 2Big 20TB is a Thunderbolt 3 dual-bay external hard drive enclosure and dock with capacity options of 8/12/16/20 TB.

The “2” in “2Big” means that two hard drives are used, the Seagate Iron Wolf series. Similarly, 6Big and 12Big are 6 and 12 bay enclosures from LaCie.

Each drive pops out elegantly and easily; simply pull the right side, which levers-out the drive in its carrier instantly. That means that users could purchase extra trays and swap drives.

The LaCie 2Big is a storage unit on the face of it, but it is in effect also one of a crop of Thunderbolt 3 docks, because it includes CompactFlash and SD card readers, a USB 3.0 port for connecting a USB device, and a DisplayPort port.

The DisplayPort port is particularly useful because it allows connecting an external display which can otherwise not be connected to a Thunderbolt 3 Mac (appropriate cable needed, not supplied), for example any of the NEC PA professional series displays and many other brands— it eliminates the need for a separate DisplayPort adapter.

  • 20TB Capacity (2 x 10TB Seagate Iron Wolf Hard Drives)
  • 2 x Thunderbolt 3 ports (allows daisy-chaining another TB3 device)
  • USB-C port (input, alternative to using a Thunderbolt 3 port for Macs with only USB-C).
  • USB 3.0 Type-A port to connect other items
  • DisplayPort for connecting a display
  • CompactFlash & SD Card Slots
  • Supports RAID 0, 1, and JBOD
  • Pre-Configured as macOS Extended RAID 0
  • Supports hardware RAID Controller via LaCie RAID Manager or software RAID via Disk Utility or SoftRAID
  • Data Transfer Speeds up to 440 MB/s ( as fast as the hard drives are capable of)
  • Up to 27W of Power for Laptop Charging
  • Windows & Mac Compatible

Vendor description

If you've been looking for a powerful and versatile Thunderbolt 3 docking station that restores many of the ports and connectivity that have been removed on modern day laptops, take a look at the 20TB 2big Dock 2-Bay RAID Array Thunderbolt 3 from LaCie.

The 2big Thunderbolt 3 Dock delivers a storage capacity of 20TB, which is comprised of two 10TB Seagate IronWolf Pro 7200 rpm SATA III 3.5" enterprise-class hard drives.

While the 2big is compatible with Windows 10 and macOS 10.12, it comes formatted as HFS+ for Mac, and is configured as hardware-controlled RAID 0, which provides performance gains, but no data redundancy. Also supported is RAID 1 and JBOD.

The back of the 2big is equipped with two 40 Gb/s Thunderbolt 3 ports and one 5 Gb/s USB 3.0 Type-C port, all of which allow you to interface with your host system at speeds up to 440 MB/s. The Thunderbolt 3 interface can also be used to connect two 4K displays or one 5K display, as well as daisy-chain up to five additional Thunderbolt 3 peripherals together. If you need to power your laptop, the USB Type-C port provides 27W of power, while the Thunderbolt 3 interface provides 15W of power for charging USB Type-C laptops. Additionally, there is a DisplayPort interface that supports 720p, 1080p, and 4K displays.

On its front, the 2big has a built-in USB 3.0 Type-A port, which can charge your USB device or connect a USB drive or digital camera for offloading files, as well as a CompactFlash and SD card slots, allowing you to directly download content from your drone, DSLR, GoPro, and more. This dock can store hundreds of hours of 4K footage and hundreds of thousands of raw images.

The LaCie 20TB 2big Thunderbolt 3 Dock includes a Thunderbolt 3 / USB Type-C cable and an external power supply. If you want to use this dock with your USB 3.0 Type-A system, a USB 3.0 Type-C to Type-A cable is also included. Protection is provided by a limited 5-year warranty.

Please Note: Thunderbolt and Thunderbolt 2 are only supported when Apple's Thunderbolt 3 (USB Type-C) to Thunderbolt 2 Adapter is used with systems running macOS 10.12 Sierra or later.

Build quality

The LaCie 2Big is a very compact and quite heavy unit, solidly built out of what seems to be heavy gauge aluminum— robust and with a feeling of high quality. The Seagate Iron Wolf drives are thus quite appropriately housed. My only gripe on build is that I’d like slightly beveled edges instead of the sharp right angled edges. But to be fair, the Apple iMac 5K has an almost cuttingly sharp bottom—try carrying it just 100 feet to an Apple Store for repair.

The rear power switch is small and this is both a plus and a minus: small enough not to accidentally turn the unit off without intending to do so (a precise touch is required), and a bit smaller and less easy to find by feel and turn on/off. Since most users are not likely to turn the unit off (it sleeps when the Mac sleeps), the design choice is good one.

I took the LaCie 2Big traveling with me in my photography adventure van, storing it within a travel box protected by two closed-cell foam pads on each end of the unit, the ones it shipped with—this worked great. [Stuff that is not secured can go flying on tight corners or with unexpected hard braking, so it would have been unwise to leave it loose on the desk inside the van, although the feet have excellent grip.] Setup is very fast—just plug in the power cable and Thunderbolt 3 cable; these I left plugged in on the desk inside the van.

OWC Thunderblade Thunderbolt SSD

Blazing fast, up to 32TB.


√ No more slow and noisy hard drives!


Shown below, the power input port with the power switch above it, dual Thunderbolt 3 ports, USB-C port (marked “USB 3.1”), and the DisplayPort. Some displays take a Mini DisplayPort cable and some take a DisplayPort cable, and some take both; the other end would need to be DisplayPort to plug into the 2Big as shown here.

Rear of LaCie 2Big 20TB Thunderbolt 3

The CompactFlash and SD card reader slots are at unit front (why is it that Apple never figures out this common sense arrangement on the iMac?). The standard USB3 type A port allows connecting a USB device of any sort—a wired keyboard for example, or a USB-A SSD and so on.

Because Thunderbolt 3 has very high bandwidth, an external SSD like the OWC Envoy Pro EX ought to run at full speed even while the LaCie 2Big is also running at full speed. See the testing section of this review for results.

Front of LaCie 2Big 20TB Thunderbolt 3

In Use


Auditory characteristics are crucial in a unit designed to be placed on a desk by many users. In this regard the LaCie 2Big add virtually no noise of its own—excellent.

The LaCie 2Big is exceptionally quiet for what it is, but it it not its very low level fan noise that can potentially be at issue—it’s any resonant vibration on certain types of surfaces, which is true of any/all hard drive units that MPG has tested. Head-seeking might also irritate some users, but there is no avoiding that with hard drives. My perspective is preferring complete silence, though even with my main store (the OWC Thunderbay 4 under my desk), I cannot achieve that.

Spinning hard drives have as a low level resonant vibration from the spinning platters. On my wooden desk, that vibration tends to resonate slightly, which is why I prefer to place all my other disk enclosures (OWC Thunderbay 4 units) under my desk on acoustic pads on the hardwood flooring—attenuating everything but fan noise. A 2-meter Thunderbolt 3 cable will afford a lot of choice in where to place the unit. Alternatively, Sorbothane pads @AMAZON do well at isolating most frequencies.

How I put it to use

Once done with the core testing, I put the 2Big to use as a monster backup drive (20GB total as a RAID-0 stripe)—perfect for my needs because I can clone all my main data drives (“master” volumes) onto the LaCie 2Big. Plus the striping doubles the speed, making backups much faster than to a single hard drive.

While LaCie supplies the LaCie RAID Manager to format and partition the unit, I used it only to the extent of making the 2Big appear as a single 20TB volume as a hardware RAID-0. For disk partitioning, I used Disk Utility, partitioned those 20TB as shown. See Cloning as a Backup Strategy.

  • 1TB MasterClone volume (a clone backup of my Master volume)
  • 300GB BootClone volume (a clone backup of my Boot volume)
  • 8.35TB ArchiveClone (a clone of my Archive volume )
  • 2.65TB TM volume for Time Machine backup, for which this capacity is ample because TimeMachine is inappropriate for large archival volumes; this volume is only for Boot and Master, the volumes that change every day. Everything else is archival or semi-archival.
  • 7.7TB ArchivePV_Clone ( a clone of my ArchivePV volume).

The nice bonus of going with 20TB is having both Time Machine *and* clones together—Time Machine runs every hour; clones re much more convenient and directly accessible (and TimeMachine has a history of bugs and being broken with new releases of macOS).

LaCie 2Big 20TB partitioned for my storage needs

Sustained performance

Tested using the fill-volume command of diglloydTools DiskTester.

Performance looks to be as fast as is possible with the dual Seagate 10TB Iron Wolf Drives—in a word outstanding with no loss of performance using the hardware RAID internal to the unit.

The dropoff in speed across the drive capacity is an universal behavior of hard drives, and nothing particular to the LaCie 2Big; all hard drives behave this way due to data density on increasingly smaller diameter inner tracks.

LaCie 2Big 20TB: sustained performance across the 2TB capacity

Speed vs transfer size

Tested using the run-sequential-suite command of diglloydTools DiskTester.

These are outstanding speeds for a hard drive. Indeed, the 32K transfers are faster than as the SSD in the 2017 iMac Pro. Note that 32K transfers make no use of RAID, but that 64K transfers and large sizes do.

The speed rises to about 470 MB/sec with larger transfers (235 MB/sec X 2) which is as fast as the hard drives can go.

LaCie 2Big 20TB: speed in MB/sec versus transfer size

Front port testing

Front USB 3.0 port

The front USB 3 port delivers the standard 900 milliamps (4.5 watts), according to Seagate/LaCie. That means that some devices will not work, because they exceed the available power draw.

On its front, the 2Big has a built-in USB 3.0 Type-A port, which can charge your USB device or connect a USB drive or digital camera for offloading files...

The built-in ports on a Mac and on some high-power hubs supply as much as 10-12 watts. Thus devices that work fine on such ports might draw too much power for the front port on the 2Big. This issue I ran into with the OWC Envoy Pro 480GB and the OWC Envoy Pro 1TB and the Samsung T5.

OWC Thunderbolt 3 Dock
Ideal for any Mac with Thunderbolt 3

Dual Thunderbolt 3 ports
Gigabit Ethernet
5K and 4K display support plus Mini Display Port
Analog sound in/out and Optical sound out

Works on any Mac with Thunderbolt 3

Compact Flash and SD slots

The front SD card slot was tested with diglloydTools DiskTester read-files command, reading gigabytes of very large image files from the exceptionally fast Lexar 2000X 64GB SDXC card.

As a reference, the SD card slot in the OWC Thunderbolt 3 Dock was also tested. Performance of the LaCie 2Big SD card slot is outstanding!

91 MB/sec OWC Thunderbolt 3 Dock
236 MB/sec LaCie 2Big
93 MB/sec built-in SD slot on 2017 iMac 5K

To validate data integrity in reading the card, diglloydTools IntegrityChecker was used. First an update was done, followed by a verify several times—no errors were seen as ought to be—perfect.


Disclosure: B&H Photo offered me this unit to keep if I agreed to review it. I agreed because it fit a need I had (and I am always in need of more space!). My review is objective and tells all of what I found and how I use it—it is a very nice unit that I am glad to have onboard in my work environment and I recommend it as an excellent choice (I don’t put gear into use that doesn’t meet my very high standards).

Get LaCie 2Big at B&H Photo.

The LaCie 2Big is an attractive and very solidly build dual-drive storage and dock unit. It is exceptionally quiet for a hard drive unit, possibly the quietest hard drive unit I have ever used. It will fit nicely on a desk and adds the attraction of two camera card slots and a USB port. That said, I prefer zero noise (not possible with hard drives), so place it under a desk using a 2 meter Thunderbolt 3 cable if you’re as sensitive as I am to noise.

As for speed and reliability, the storage aspect operated flawlessly, the card reader speed is outstanding. The only negative is the to-USB-spec power of the USB port (900 mA), which is too little to power some external devices, like certain USB SSDs.


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