Okay so.. In a nutshell I'm curious about factors that could impact External SSD speeds over USB3/3.1. I'm posting this here specifically since my experiences have ranged between Sierra, HS, and Mojave, with various USB3 and USB3.1 enclosures, and two different Samsung SSDs, an 840 Pro 256GB, and a brand new 860 Evo 1TB, and two different macs. Im hitting what I can only describe as a "Speedwall" when testing via BlackMagic, or even testing actual file transfers monitoring the R/W speeds between drives with iStat. My Read speed wall is 430mbps, and write speed wall is 420mbps. Doesn't seem to matter which drive or enclosure I used (I have several) nor which device I test on (2018 Mini or 2013 MBP, both currently running Mojave). I can not seem to go above those speeds. I had the same speed limitations with the 840 Pro on the Macbook pro in Sierra and HS, HFS+ and now w/ APFS. Its super odd to me. I can't seem to get the write speeds samsung reports when using SSD externally on MacOS. That same 840 Pro on windows hits over 560mbps. Even this brand new 860 Evo 1TB I just received today, when plugged into a USB3.1 Gen2 enclosure maxes out at 430mbps/420mbps, whether I use HFS+ or APFS. Any ideas as to what could be causing this? --- Post Merged, Apr 15, 2019 --- Here are two benchmarks results tested just now. The first is the new 1TB 860 EVO, the second is the 256GB 840 PRO. Both seem to hit the same wall as I explained above. The 1TB is in a Vantec USB 3.1 gen2 enclosure. The 256GB is in a Sabrent USB3.0 enclosure. But Ive tried either SSD in either enclosure, same results. I've tried other enclosures I have as well, same results. All my enclosures are USB3.0, with the one Vantec being 3.1 gen2, but that shouldn't even matter as USB3 should be enough to support R/W's at the suggested Samsung speeds 550/520, no? I'm wracking my brain with this! Any help would be appreciated! Thanks in advance.