The Intenso 2.5’’ SSH High is a very low quality drive.
The datasheet specifications say up to 520 MB/s reading and 480 MB/s writing. However, the real speed is much lower than that because the high speed is only due to an internal RAM of about 4 GB which is used for the cache. Hence it is only the transfert to this RAM so you will reach the port max speed limit.
The real inside speeds are as following : Read = 122 MB/s (196s for 23913 MB) Write = 33.2 MB/s (719s for 23913 MB)
With these speeds, you need to wait 4000 / 33 = 121s = 2 minutes until the internal write cache is cleared. So as long as this 4GB write cache is not filled, you can write at 386 MB/s. But as soon as it is full, the write speed will drastically drop down to minimum 5.5 MB/s, with usually a mean write speed of 33MB/s. The same for reading. At beginning the first 3 GB are at a speed of 407MB/s, then it drops to 122 MB/s mean read speed. This limitation seems to be firmware capped as there is no reason for that limit else.
So this drive is good only if you need to write quickly some files but not for a full transfer of more than 3 to 5 GB as the specified speed will not be reached and only the lowest real values indicated here will be met.
Absolute max speeds (to/from a RAM disk): Read = 407 MB/s Write = 386 MB/s