On Fri, Jun 17, 2016 at 07:41:26PM +0200, Michael Schaller wrote: > Alan, thank you for the analysis and you are correct in your > assumption that this is a plain dumb thumb drive. The puzzling thing > for me is that the drive only shows this bottleneck under Linux and > not under Max OS X or Windows. Here are my results for Linux vs. Mac > OS X again: > > Write speed under Linux: > $ sudo dd if=/dev/zero of=/dev/sdb bs=1M count=256 > 256+0 records in > 256+0 records out > 268435456 bytes (268 MB) copied, 5.98705 s, 44.8 MB/s > > Write speed under Mac OS X: > $ sudo dd if=/dev/zero of=/dev/rdisk2 bs=1048576 count=256 > 256+0 records in > 256+0 records out > 268435456 bytes transferred in 0.941998 secs (284963933 bytes/sec) > > Alan, do you have any idea why the write speed differs so heavily > between Linux (~45 MB/s) and the other OSs (~270 MB/s)? Could the > initialization of the flash drive be different under Linux and the > other OSs? Are you sure the write is finished for both of these? Please do a 'sync' afterwards to flush the buffers to the device. Note, I don't know if OS-X does do sync properly, you will have to determine that, perhaps by trying to eject the device cleanly. greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
