I have a USB 3.0 flash drive plugged into a 2.0 port (I understand that this makes 3.0 functionality meaningless), and when copying a file from the flash drive to the computer's hard drive (5400 RPM HDD), it copied at around 15 to 20 MB/s, while copying the same file to the flash drive it was originally on was around 10 - 11 MB/s. But wouldn't copying the file to the flash drive make it so that the file doesn't need to go through the computer, meaning the flash drive can use its higher speeds due to the 3.0? Why was it slower than copying to the HDD?
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Speed of copying or moving files from one device to another is all governed by a number or things and one of them is the read and write speeds of the relevant devices. They can only operate (at a maximum) at the lowest comparative speed. Say device 1 reads at 54mb/s and device 2 writes at 32mb/s then the speed will be limited to 32mb/s. Another way it can be slowed down is when any background operations are going on at the time (virus checking software etc.)– Chris RogersDec 6, 2016 at 0:07
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Flash drive and HDD are PERIPHERAL DEVICES to computer. The term "peripheral" explicitly expresses the fundamental data transfer topology: read from peripheral -> transfer to host -> write to peripheral. There is no other path in PC. Peripheral devices do not write anything internally, directly to itself. They communicate only from "periphery" to "center", and vice versa.
Even if the flash drive is capable of USB 3.0 speeds, it can achieve these transfer rates only when connected to a corresponding host port.
The copy procedure is READ, then WRITE. If you transfer data from flash to HDD, the transaction proceeds faster simply because the HDD writes are much faster than the write speed of flash drive. So the time to WRITE to HDD is smaller than if the system writes it back to the same flash at USB2 rates.
answered Dec 6, 2016 at 1:09
