Greg, for my initial tests I did a sync afterwards and it finished immediately on Linux and Mac OS X. Sorry for not mentioning that earlier. Furthermore 270 MB/s is the advertised write rate of the flash drive. Mac OS X and Window can both write at the advertised speed and Linux only reaches ~45 MB/s (~1/6th). If someone is interested into digging deeper into this issue I can look into shipping one of these flash drives... On Fri, Jun 17, 2016 at 8:30 PM, Michael Schaller <misch@xxxxxxxxxx> wrote: > Greg, for my initial tests I did a sync afterwards and it finished > immediately on Linux and Mac OS X. Sorry for not mentioning that earlier. > Furthermore 270 MB/s is the advertised write rate of the flash drive. Mac OS > X and Window can both write at the advertised speed and Linux only reaches > ~45 MB/s (~1/6th). > If someone is interested into digging deeper into this issue I can look into > shipping one of these flash drives... > > On Fri, Jun 17, 2016 at 8:23 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> >> 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
