I was attempting to copy some files over from an external drive today and noticed how very slow the files were being transferred from the external drive to my PC - just about 800KB per second. PC is running Ubuntu 11.10.

With my other PC, which is running Fedora 15, I can transfer/copy files (from the same external drive) at decent rates i.e., around 30MB/s.

Does anybody know how I can fix this?

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I removed all items connected to the other USB ports on this machine (a laptop) and now the transfer rates are back to normal i.e. averaging around 30MB/s.

The other items attached to the laptop were:

1. Wireless Mouse
2. Laptop cooler fan (just drawing power, I suppose).

I will investigate this further in the future perhaps, but for right now I am not interested to know how and why this can happen. I am just happy I got it "fixed."

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IIRC, if you have a USB 1.x device connected to a USB 2.0 hub, the hub will throttle all data to match the slower device. Assuming the USB ports on your computer are all connected to the same hub chip internally, your data transfer will be at 1.x speeds because of the mouse, regardless of the capabilities of the drive. I believe this is to ensure the slower devices don't get lost in the signal, or something like that.

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Thank you for your comments, crystalattice.

That was also my suspicion at first. But today I know it is a bit more complicated than that. Ever since the upgrade (to Ubuntu 11.10,) many things related to USB on this machine has become unreliable. Like, recently I noticed the webcam not working occasionally... which is something new since the upgrade.

From my observation, everything appears to work as long as I have just booted the machine. If, however, I suspend the laptop and bring it back up, then every USB port seems to work slowly and the webcam will not work as it should. So, for now, I just reboot the laptop if I need anything that requires USB ports to be working optimally.

If someone reading this someday has a solution, I will be grateful for the share.

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