Live 14.04 system locks up under heavy I/O with external NTFS-formatted usb2 drives

[Daniel Kulesz]

Hi folks,

I was happy to see that Lubuntu 14.04 Live is booting up fine on my
aged Thinkpad X40 (1,2 GHz Pentium-M with 1GB of RAM). Unfortunately,
the tasks for which I intended to use the machine are not working the
expected way. I experienced two failures / bugs:

- PCManfm is pretty stupid at calculating the remaining time for a
file operation: when copying one 500 GB file from one connected
USB2-Drive (ext4) to another (ntfs), it started calculating the
remaining time for more than 10 minutes (I aborted it then) and it did
not begin the copy process until then. Seems like it was first trying
to read the complete file before starting the copy process? Makes no
sense for me, using "cp" on the command line it worked fine, although
the system seems to have locked up in the end (completely
unresponsive) so I had to shut it down by force. Comparing the md5sum
of the two files, the copy operation seems to have been successful
though.

- the system locks up: in a second attempt, I tried to copy around 700
GB of small files/folders from one connected USB2-Drive (ntfs) to
another (also ntfs). The copy process went fine for about 20 minutes,
then there was no visible progress. Switching to command line reveiled
that 99% CPU was in "wa", and the logs contained some "ntfs driver
waiting for longer than 120 seconds" messages, together with some
stack trace. There were about 70MB of memory free though. Logging into
two consoles and running "uname -a" in one of them left the system
completely unresponsive, even a reboot was not working anymore.

Sorry that I have no logs to attach, but I hope this fault can be
easily reproduced in a virtual environment as well. To me, it seems
like either the ntfs driver or the usb subsystem seem not to be able
to work reliably in "low memory" conditions, although I think it's
debatable if 1GB is really "low". I expect things to be slow, but not
to lock up!

Cheers, Daniel