How to troubleshoot slow USB2.0

Question

I'm running Ubuntu 11.10 64-bit and writing to a USB 2.0 device is very slow. I have two USB hard drives and two USB keys that I've tried. I've tried using nautilus drag and drop, cp, and rsync commands to transfer a roughly 800MB video file (to test all of the drives). I run iostat -k 5 while the file is transferring and I see a write speed of around 4000-5000 kB_wrtn/s.

I've used disk utility to confirm that the drives are recognized as USB 2.0 drives. I've tried the drives in all of the USB ports on the back of the machine.

I will happily edit this question with more information if anyone can tell me what information I should be looking for or commands I should run to debug this issue.

Answer 1

I know answering your own questions is generally frowned upon... and I'm still not exactly sure how to trouble shoot USB problems (which is really what I wanted to know), but the following seems to have fixed my problem:

Add pci=routeirq to the linux boot command. I.e. I have a custom grub entry in /etc/grub.d/40_custom like this (note I copied and pasted the default entry from /boot/grub/grub.cfg and then added pci=routeirq):

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry 'Ubuntu, with Linux 3.0.0-14-generic, PCI=routeirq' --class ubuntu --class gnu-linux --class gnu --class os {
    recordfail
    set gfxpayload=$linux_gfx_mode
    insmod gzio
    insmod part_msdos
    insmod ext2
    set root='(hd0,msdos3)'
    search --no-floppy --fs-uuid --set=root 9701201a-c029-4d58-b44a-1dc208ca03b1
    linux   /boot/vmlinuz-3.0.0-14-generic root=UUID=9701201a-c029-4d58-b44a-1dc208ca03b1 ro   quiet splash vt.handoff=7 pci=routeirq
    initrd  /boot/initrd.img-3.0.0-14-generic
}