Testing Sonnet's Fusion Flex J3i Mount With the Mac Pro

Sonnet earlier this year announced the launch of the Fusion Flex J3i internal drive mount, which is designed to let users add up to three SATA storage drives to the 2019 Mac Pro.


In our latest YouTube video, we went hands on with the Fusion Flex J3i, hooking it up to our ‌Mac Pro‌ to see how it performs.

The Fusion Flex J3i is a mount system that can provide up to 36TB of additional storage for the ‌Mac Pro‌. When purchased from Apple, the ‌Mac Pro‌ maxes out at 8TB of storage, so Sonnet's add-on provides a huge storage boost. The storage added through the Fusion Flex J3i will not, of course, act as a main boot disk and will instead work like an external drive that's plugged into the Mac.

You don't get any storage with the Fusion Flex J3i since it's designed to be a mounting system, so you're going to need to purchase storage separately and add it yourself. The Fusion Flex J3i supports two 3.5-inch drives and one 2.5-inch SSD or three 2.5-inch SSDs.

We tested the Fusion Flex J3i with two 4TB 3.5-inch hard drives from Western Digital, and installation was simple. Just four screws attach each of the hard drives to the J3i after the SSD plates have been removed.

After the Fusion Flex J3i has been outfitted with SSDs or hard drives, it also takes just a few minutes to get it up and running in the ‌Mac Pro‌. Pull off the cover, unscrew the plate at the top, and then insert the J3i into the machine.

The hard drives will connect to the ‌Mac Pro‌ and then you can attach the three SATA cables that come with the J3i, and since the ‌Mac Pro‌ has 1, 2, and 3, labeling, it's pretty easy to tell what goes where. After the mount is in place, put the ‌Mac Pro‌ back together, boot up, and all should be working well.

We found the Fusion Flex J3i to be a useful plug and play solution for those who are looking to add additional storage to their ‌Mac Pro‌ machines, and it's also cost effective. Sonnet charges $199 for the Fusion Flex J3i, and while adding storage is expensive, it's still cheaper than buying Apple's higher-tier SSD storage options.

You can get two 16TB 3.5-inch drives from Amazon for around $800, for example, which gives you 32TB of storage for much less than the $2,600 upgrade fee for the 8TB SSD from Apple. SSD storage is faster, of course, so if you want to go that route, you can get 4TB SSDs for somewhere around $600 each, which still comes in cheaper than Apple's storage.

For our setup, we have a couple PCIe SSDs in the ‌Mac Pro‌ for video editing purposes, with the J3i on hand for storing larger files, RAW images, and video backups.

Sonnet's Fusion Flex J3i can be purchased from the Sonnet website for $199.

Tag: Sonnet

Top Rated Comments

XXPP Avatar
7 months ago
$199? For a piece of bent sheet metal? For that I can buy a whole good PC case. Someone is crazy.
Score: 5 Votes (Like | Disagree)
darthaddie Avatar
7 months ago


probably something to do with low volume production

more like milking the Mac Pro group.


with a 1000 unit minimum it shouldn’t cost most than $10-$15 (even less) to Manufacture and import into the US. I have been in manufacturing in China and that’s all it takes. I would rather invest in a DAS with 4-5 bays.
Score: 4 Votes (Like | Disagree)
erniefairchild1 Avatar
7 months ago


[IMG width="251px"]https://images.macrumors.com/images-new/macrumorsthreadlogo@3x.png[/IMG] ('https://www.macrumors.com/2020/07/08/sonnet-fusion-flex-j3i/')

Sonnet earlier this year announced the launch ('https://www.macrumors.com/2020/05/27/sonnet-fusion-flex-j3i-mac-pro/') of the Fusion Flex J3i internal drive mount, which is designed to let users add up to three SATA storage drives to the 2019 Mac Pro.


Subscribe to the MacRumors YouTube channel ('//www.youtube.com/user/macrumors?sub_confirmation=1') for more videos.

In our latest YouTube video, we went hands on with the Fusion Flex J3i, hooking it up to our Mac Pro to see how it performs.

The Fusion Flex J3i is a mount system that can provide up to 36TB of additional storage for the Mac Pro. When purchased from Apple, the Mac Pro maxes out at 8TB of storage, so Sonnet's add-on provides a huge storage boost. The storage added through the Fusion Flex J3i will not, of course, act as a main boot disk and will instead work like an external drive that's plugged into the Mac.

You don't get any storage with the Fusion Flex J3i since it's designed to be a mounting system, so you're going to need to purchase storage separately and add it yourself. The Fusion Flex J3i supports two 3.5-inch drives and one 2.5-inch SSD or three 2.5-inch SSDs.

We tested the Fusion Flex J3i with two 4TB 3.5-inch hard drives from Western Digital, and installation was simple. Just four screws attach each of the hard drives to the J3i after the SSD plates have been removed.

After the Fusion Flex J3i has been outfitted with SSDs or hard drives, it also takes just a few minutes to get it up and running in the Mac Pro. Pull off the cover, unscrew the plate at the top, and then insert the J3i into the machine.

The hard drives will connect to the Mac Pro and then you can attach the three SATA cables that come with the J3i, and since the Mac Pro has 1, 2, and 3, labeling, it's pretty easy to tell what goes where. After the mount is in place, put the Mac Pro back together, boot up, and all should be working well.

We found the Fusion Flex J3i to be a useful plug and play solution for those who are looking to add additional storage to their Mac Pro machines, and it's also cost effective. Sonnet charges $199 for the Fusion Flex J3i, and while adding storage is expensive, it's still cheaper than buying Apple's higher-tier SSD storage options.

You can get two 16TB 3.5-inch drives from Amazon for around $800, for example, which gives you 32TB of storage for much less than the $2,600 upgrade fee for the 8TB SSD from Apple. SSD storage is faster, of course, so if you want to go that route, you can get 4TB SSDs ('https://www.amazon.com/Samsung-Inch-Internal-MZ-76E4T0B-AM/dp/B07864XY8B') for somewhere around $600 each, which still comes in cheaper than Apple's storage.

For our setup, we have a couple PCIe SSDs in the Mac Pro for video editing purposes, with the J3i on hand for storing larger files, RAW images, and video backups.

Sonnet's Fusion Flex J3i can be purchased from the Sonnet website ('https://www.sonnettech.com/product/fusion-flex-j3i/overview.html') for $199.

Article Link: Testing Sonnet's Fusion Flex J3i Mount With the Mac Pro ('https://www.macrumors.com/2020/07/08/sonnet-fusion-flex-j3i/')

I can‘t wait to find out what MacRumors commenters decide to complain about on this one!
Score: 4 Votes (Like | Disagree)
Ronlap Avatar
27 weeks ago
I ordered this the first day it was available and it should be here tomorrow. This is insanely cheap compared to the Promise Pegasus, which comes with an 8TB drive that apparently everyone sells on eBay. I will be installing two 12GB Hitachi Helium disks to use for Time Machine and maybe an SSD as a scratch disk. My in-use video files sit on a Sonnet PCI card which holds four 2TB 970 EVO Plus NVMe SSDs while the rest of my files sit on Thunderbolt 2 storage arrays outside the box.


LOL the 2.5" SSD is using a SATA to USB adapter bahahahah... What a kludge.

Ya work with what Apple gives you and that's the only free port after the two SATA ports are used. I am not sure why someone can't figure out how to daisy chain those.
Score: 3 Votes (Like | Disagree)
yurc Avatar
27 weeks ago
Heya, those drive cage should be included in Mac Pro from very beginning as default configuration, users can removed it if doesn’t need SATA disk. If Apple adopt this idea from 5,1 era it would turn selling Mac Pro without including any drive sleds.


The shape is so simple, it should be relatively easy to 3D print an enclosure for these drives. It's just the dang weird power cable that I'd have no idea how to source.

Some of our folks already making 3D prints for DIY drive cages, DIY power cable is also done to avoid crazy Belkin cable price.

It seems all 7,1 oriented peripheral are indeed, overpriced for such basic cable drive cage, in the name of ”for pro” machine sake.
Score: 2 Votes (Like | Disagree)
R3k Avatar
7 months ago
Hmm, i purchased and installed a Sonnet Tempo PCI-E Card that mounts 2 x SSD drives inside the 2019 MP.

This card cost $99 ('https://www.bhphotovideo.com/c/product/893304-REG/Sonnet_tsata6_ssd_e2_TEMPO_SSD_THUNDERBOLT_COMPATIBLE.html')
Score: 2 Votes (Like | Disagree)

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