San Disk Cruzer - File Transfer Speeds

File Transfer Speeds

USB flash drives usually specify their read and write speeds in megabytes per second (MB/s); read speed is usually faster. These speeds are for optimal conditions; real-world speeds are usually slower. In particular, circumstances that often lead to speeds much lower than advertised are transfer (particularly writing) of many small files rather than a few very large ones, and mixed reading and writing to the same device. In a typical well-conducted review of a number of high-performance USB 3.0 drives, a drive that could read large files at 68MB/s and write at 46MB/s, could only manage 14MB/s and 0.3MB/s with many small files. When combining streaming reads and writes the speed of another drive, that could read at 92MB/s and read at 70MB/s, was 8MB/s. These differences differ radically from one drive to another; some drives could write small files at over 10% of the speed for large ones. The examples given are chosen to illustrate extremes.