Question M.2 NVMe external cases limit of 2TB - does it really exists and if yes: why?

Jan 28, 2021

I am recently once again upgrading my local storage capacities. For many reasons I wanted to add a third M.2 NVMe drive - but this time connect it via a cable of some sort and not install it in a dedicated M.2 slot on my motherboard. And so I started looking for solutions. Long story short: to my surprise it seems that there are no [at least single drive] cases that can host a drive in size of 4TB. And those who are suppose to utilize 20 Gbit/s bandwidth [with USB-C connector / 3.2 Gen 2×2 ] are scarce - as most will of such cases can give you only 5 or 10 Gbit/s [USB-A / 3.2 Gen 1×1 or 3.2 Gen 2×1 ]

The offers on vendors sites often say nothing about limitation in regards to drive size. But when I looked for detailed info on manufacturers sites, in the datasheets there were annotations like "up to 2 TB". And so I asked one of them is that a correct and still valid info - and they said yes. When I asked why, they said that "over 2TB the power requirement of the SSD is greater than what USB can deliver"- as they were referring to the Type-C of USB. So I asked about the Thunderbolt 3 [40 Gbit/s] technology : "Will such case products made with Thunderbolt 3 as a connection method will be able to run NVMe drives bigger then 2 TB? And if yes- are you planning to make such in a foreseeable future?". And they replied that it would not make sense because "we can't sell any significant numbers of it" because such big NVMe drives are too expensive. The problem is supposed to be of both the hardware nature and that of licenses. So I tried to asking the next logical question: "If USB-C is to weak then will it be possible with Thunderbolt3 - and customers simply have to wait until the prices of such drives come down, so that then the manufacturers like yourself will start making cases with Thunderbolt 3 connection?". Unfortunately they do not want to answer that directly, leaving me stranded

And so: what are your thought on that? I tried googling various "2 TB limit" in regard to drives but all I found were some old threads here and there in regards to SATA SSDs and even HDDs. The conclusion from them were among the lines of: costs of license, limitation of old operating systems and tests made with biggest available drives at that time [which happened to also be 2 TB]

All in all I want to buy such case with a 2 TB even with a size cap and put in it my "old" M.2 NVMe 1 TB drive - while on the motherboard in the now emptied slot I will put a brand new 4 TB NVMe. But can motherboards have such limitations as well? The manual for mine says nothing of that kind - but you never know, right? I am afraid that I will buy an expensive piece of hardware that I will be unable to use in any way

As for the root of the problem. I would have never guested that the it was the unbeknownst to me limitations of USB-C - that it cannot supposedly power anything above 2TB. I was rooting for:

A] not advanced enough hardware of in the case itself

B] lack of drivers in that hardware as the implemented ones were written were there were only 2 TB drives available

C] some kind motherboard / BIOS limitations of similar as above either hardware or software nature

And overall: I was thinking that they were just playing it on the safe side; i.e. that the datasheets were published after test being made on biggest drives of that kind [2 TB] available on the market at the time of their execution - and so they did not wanted to upgrade the information without making new sets of tests


Can't imagine it being a power limitation, not like the larger drive is necessarily more power hungry. Comes down to the controller speed and the flash chips power consumption. Not an addressing limitation, since USB, PCIe, Thuderbolt, etc are all serial connections.

Sabrent is selling this alongside 8TB drives, I assume it would work.