Ubuntu
gvfs package

  1. Bug #197762
  2. Comment #140

Comment 140 for bug 197762

Revision history for this message
Ulrich Lukas (ulrich-lukas) wrote : Re: file transfers on USB disk are very slow

System running Ubuntu Jaunty AMD64, vanilla 2.6.29.1. KDE4.2, two terminal windows, no other graphical applications.

I created two test files of identical size with random data and copied to the USB pendrive, once on a freshly rebooted system, and once after I first experienced a slowdown while copying some other files to the pendrive and deleting them again; doing a "sync" after each copy.
A second terminal window ran dstat -D sda,sdb both times.

( Preparation:
dd if=/dev/urandom of=/var/tmp/850-MiB-testfile.A bs=1M count=850
dd if=/dev/urandom of=/var/tmp/850-MiB-testfile.B bs=1M count=850
reboot )

First run after reboot:
(/dev/sdb1 mounted on /media/pendrive)
cp /var/tmp/850-MiB-testfile.A /media/pendrive

Second run after the first slowdowns were observed during copying of other files and deleting them again:
cp /var/tmp/850-MiB-testfile.B /media/pendrive

The output results of "dstat -D sda,sdb" are attached.

First run, approx. 16 MiB/sec constant: dstat-D.OK.850-MiB-random-data.txt

Second run with slowdown: dstat-D.slow.850-MiB-random-data.txt

I'm sorry, I couldn't figure out what causes the slowdown after a while.

I'm doing some more tests tomorrow, with other kernel versions
and with a borrowed USB harddisk.