On Fri, 5 Jun 2015, Mark Hills wrote: > I have a new USB 3.0 hard drive which appears to be throttled at > approx 5Mbyte/sec. > > Is there a mystery kernel option that is required to enable full > performance on these new drives? > > I have tried changing following: > > * Switching onboard USB 2.0 interfaces for a completely new USB 3.0 > interface (xhci_pci) > > * Enabling and disabling the "USB attached SCSI" CONFIG_USB_UAS > > But drive performance stays limited at 5Mbyte/sec. > > I've settled on using the USB 3.0 interface, and the dmesg (below) reports > "SuperSpeed" and looks ok. > > - The system is kernel 4.0.4 i686, on an HP xw6600 > - Drive is a "Seagate Backup Plus for Mac" > > The drive does work on a separate Linux system -- 145Mbyte/sec (albeit > only intermittently detecting the drive). That rules out any bad disk > format or block alignment. In this case it is a Thinkpad X230, Slackware > kernel 3.14.23, x86_64. > > I've compared kernel configs and nothing obvious has caught my attention > in the USB/storage options. > > Unfortunately these are quite different systems that prevent me testing an > identical kernel. > > Is anyone aware of what kernel difference this might be, or could it even > be a bug on 32-bit systems? By any chance, do you mount the filesystem with the "-o sync" option? That will slow things _way_ down. If that's not the answer, try acquiring usbmon traces on the fast and slow systems for comparison (see the instructions in Documentation/usb/usbmon.txt.). Alan Stern -- 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
