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I want to purchase an external SSD for MBP 2019, 16" and occasionally run it from an external SSD. I understand that Thunderbolt 3 is much faster in data transfer than regular USB Type‑C, but can the SSD utilize this difference? Should I pay extra for Thunderbolt 3 external SSD or if I purchase a USB Type‑C SSD, then I will not feel the any difference?

Another consideration is back compatibility with older hardware. If I understand correctly, USB Type‑C <=> USB 3.0 adaptor is a much cheaper and more widely available than a Thunderbolt 3 <=> USB 3.0 adapter.

For example, I hesitate between the Samsung X5 Portable SSD (actually, it is the only one external SSD which is available near me locally) or the Samsung T7 portable SSD.

I am using my MBP for development, multiple docker containers, IDE, etc...

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  • "I understand that Thunderbolt 3 is much faster in data transfer than regular USB Type‑C" – This statement doesn't really make sense. USB Type-C is a connector, Thunderbolt 3 is a protocol (which BTW uses the USB Type-C connector). It doesn't make sense to compare them, and in particular, it makes no sense to talk about the "speed" of USB Type-C, since the USB Type-C connector can be used for lots of things, including but not limited to 1.5 Mbps USB 2.0 and 40 Gbps Thunderbolt 4. Sep 12 at 20:12
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Below are answers and comments based on the OP's posted question.

I understand that Thunderbolt 3 is much faster in data transfer than regular USB Type‑C, but can the SSD utilize this difference?

Thunderbolt 3 is up to 40 Gb/s and USB 3.1 Generation 2 is up to 10 Gb/s. The SSD used in both the Samsung T7 and X5 Portable SSDs is faster than 10 Gb/s. Therefore, the SSD can utilize this difference.

Should I pay extra for Thunderbolt 3 external SSD or if I purchase a USB Type‑C SSD, then I will not feel the any difference?

The Samsung X5 Portable SSD will be notably faster than the Samsung T7 portable SSD. Also, the Samsung X5 will appear as a NVMe drive with TRIM support just like the internal drive already in your Mac. Although, the internal drive will be slightly faster than the Samsung X5. The Samsung T7 portable SSD will appear as a USB drive. I have not found any indication that the Samsung T7 has TRIM support.

Another consideration is back compatibility with older hardware. If I understand correctly, USB Type‑C <=> USB 3.0 adaptor is a much cheaper and more widely available than a Thunderbolt 3 <=> USB 3.0 adapter.

The USB Type‑C <=> USB 3.0 adaptor is just a cable. This cable is included with the the Samsung T7 portable SSD. I am not sure a Thunderbolt 3 <=> USB 3.0 adapter that would connect a Samsung X5 Portable SSD to a USB 3.0 port exists.

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  • On a side note as a matter of interest, I run a full Windows install on a Samsung T5 SSD and I can't tell a difference between the T5 and the internal SSD of my Macbook Pro 2016. It is amazing that you can now have external I/O running at a (near) native speed.
    – s3_gunzel
    Sep 12 at 0:28
  • @s3_gunzel: Do you know the model identifier for your 2016 MacBook Pro? Sep 12 at 1:28
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It all depends. There is no good answer on if you will notice the speed difference, it just depends.

When it comes to backward compatibility you should not sweat that too much. Apple's USB-C ports with TB3 and USB4 will be backward compatible with USB 3.2, 3.1, 3.0, 2.0, and 1.1. I have not seen a TB3 drive that wasn't backward compatible with USB 3.x excepting those big RAID boxes that have some fancy SATA controller under the hood or something.

I've seen USB-C drives become hit and miss when plugged into some USB-A ports because of a lack of power and/or they can't drop down to USB 2.0 mode. If it's a matter of power then a relatively inexpensive powered USB 3.x hub can fix that. If it's a lack of Thunderbolt or USB 3.x then that is fixable now with a more pricy Thunderbolt hub. I'm experimenting with a TB4 hub on a TB2 host with the intent to get the most out of my USB-C devices, and it's not going as well as I hoped. I'm only getting USB 3.0 speeds when I should be getting TB2 and USB 3.1 speeds. It appears to be a software issue that I need to work out.

When it comes to speeds I'll be imprecise with the naming conventions but y'all should know what I mean. USB 3.0 = 5 Gbps USB 3.1 = 10 Gbps USB 3.2 = 20 Gbps USB4 = 40 Gbps TB1 = 10 Gbps TB2 = 20 Gbps TB3 = 40 Gbps

Because USB and TB encode the data differently they are not quite one to one, TB is slightly faster. Don't pay as much attention to the external interface as it will be the internal interface on the drive that will tell you how fast the drive is. I recall seeing TB3 drives but one had SAS-4 at 22.5 Gbps internally but the other was SATA Express at 16 Gbps.

There's the host controller, the drive, the drive container with it's interface adapter, then comes the cable.

Unless you are going out of your way for an active cable, which will cost a bit more than passive cables, the cables will be relatively inexpensive and their data capability easily identified. Any passive 2 meter USB cable will be capable of only USB 2.0 speeds. They may have USB-C ports on each end and allow a Thunderbolt drive to connect to a Thunderbolt host, but the data will move at USB 2.0 speeds. That may be handy if you don't need to move a lot of data and all you have is the cord that you were using to charge your laptop.

Any USB cable with USB-A on one end may be helpful as well to connect a USB-C drive but depending on the cable it will be limited to USB 2.0 to USB 3.1 speeds. USB-A has half the high speed data pins as USB-C and so tops out at 10 Gbps.

Cables of a meter in length, USB "trident" symbols on the connectors, and USB-C connections on both ends should be able to get 5, 10, or 20 Gbps. There may be a number indicating the speed in Gbps but consider that a minimum since the spec changed so quickly and allowed for cables that met the old 5 Gbps standard to meet the newer 20 Gbps standard.

USB-C cables that are about 3/4 meter in length should be capable of the highest speeds USB-C offers. Some of the cheaper cables will have no markings but should still work but cables certified for 40 Gbps will have the Thunderbolt icon with a number 3 or 4, and or a USB trident icon and a 20 or 40.

I know this is long but the point is to lay out the different bits and how they can affect the performance. If we assume a MacBook Pro with Thunderbolt 3 or USB4 then you have a host capable of supporting drives from USB 1.1 to TB4/USB4, 1.5 Mbps to 40 Gbps. On the other end is the drive, and knowing what that drive can do is a matter of looking at specs, and maybe reading some reviews. In the middle will be the drive enclosure and the cable. Chose those to match your host and drive.

That may be more than you need to know but I hope it helps.

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