[ubuntu-in] USB Mass Storage unmount bug

[Gora Mohanty]

On Sat, 2007-09-22 at 13:49 +0530, Priyadarsan Roy wrote:
[...]
> I have an external HDD connected via USB and a 1 GB pen drive most of
> the time to my system. I have copied data to and fro in the ranges of
> 4GB and above. Once in a while I have seen the machine getting stuck.
> One work around I have found is after copying large data, before I
> eject I run "sync" from the command line. This command might take some
> time to finish. You can see the Pen Dirve LED blinking fast at this
> time. After this if I eject my Laptop never used to Hang. 
[...]

Copying 4GB of data to a USB disk will take a long time, even
with USB 2.0, and the actual transfer will almost certainly be
cached. When you go to eject the drive, the transfer becomes
forced, and the immediate copying of large amounts of data
takes over your system. So, I suspect that the system is not
really hanging, but only unresponsive. You can check this by
running 'top' in a terminal window before the eject, and you
should see 'cp' starting to take up a lot of system resources
on ejecting the USB disk. If you see the list of processes in
'top' updating, that is also a sign that the system is not
hung.

When you use 'sync' as mentioned above, that forces the system
to actually transfer any pending files. So, in effect you are
doing what the system does automatically when you do an eject
without syncing.

Regards,
Gora