Problems with disconnecting USB drives

[Jeff Layton]

  On 08/31/2011 09:46 AM, James Tappin wrote:
> On Tue, 30 Aug 2011 16:53:18 -0400
> Jeff Layton<laytonjb at att.net>  wrote:
>
> JL>    Good afternoon,
> JL>
> JL>  I'm running Kubuntu 11.04 on a USB hard drive connected to a
> JL>  4-port USB hub to my laptop (this way I can run Linux on my
> JL>  work laptop when I need to :)  ). I've got another USB drive
> JL>  that is formatted as ext3 and contains some data I want to access
> JL>  from the laptop when I'm booted into Kubuntu. Every time I
> JL>  plug the drive into the hub I get the following error message
> JL>  in the system logs:
> JL>
> JL>  [ 161.254142 ] usb 2-1.1.2   USB disconnect, address 7
> JL>
> JL>  At this point I can no longer access the Kubuntu drive and the
> JL>  system ends up freezing at some point because the drive is
> JL>  not longer there. I've waited for a long time (15 minutes) to see
> JL>  if it's doing USB device discovery but no joy.
> JL>
> JL>  I surfed around the net a little but didn't see any apparent ways
> JL>  to fix this. Any ideas?
>
> I bit of a guess but:
> Are the drives powered from the USB bus or from separate supplies?
> (Likewise the hub?) It is possible that if everything is powered from
> the laptop's USB port there's not enough power and it loses the drive.
>

I never thought of that possibility. I've never seen that before.
So this assumes that the added device draws more power than
is available and causes the shutdown of the first device.

I tried an experiment to see if it was Kubuntu. I plugged the
devices into the USB hub under Windows just to see what would
happen. You are correct. When the first drive is plugged and
getting power, plugging in the second drive shuts down the
first drive. I still see the power light on the first drive but the USB
hub light for that port goes black. So I'm assuming this means
too much power.

Thanks for the idea! Now I just need to figure out how to power
these devices externally :)

Thanks!

Jeff