I've always used bs=4M for writing .iso or .img files to USB flash drives, as it gives me the best times. This is on Linux, OpenBSD, and macOS (using /dev/rdisk

I've always used bs=4M for writing .iso or .img files to USB flash drives, as it gives me the best times. This is on Linux, OpenBSD, and macOS (using /dev/rdiskn for the latter two).