High CPU usage when copying files to USB mass storage device

[Patrick O'Callaghan]

On Tue, 2011-07-05 at 17:01 +0800, 某因幡 wrote:
> Hi,
> I've tried to copy some different files to an USB flash disk and an USB HDD
> and tried different USB hubs.
> After a while the system gets very slow, switching between windows can take
> quite a while. The copying speed is slow, too(only several MB/s to an empty
> USB HDD).
> The machine is not old, just bought it this year. And on the same machine
> the same problem is not seen on Ubuntu 10.04 and Windows 7.
> Any ideas?

Flash and HDD are two different cases. Flash drives can become slow
because of their internal architecture, fragmentation, wear leveling
etc. (lots of info on this via Google). I use an 8GB pen drive a lot and
every so often find it useful to reformat it completely, which seems to
help. This is a VFAT drive since it has to be compatible with another
(non-Linux) system.

In the HDD case, you may just have a slow USB port. Check if it's USB-1,
USB-2 or USB-3 (unlikely at the moment). And remember that USB doesn't
do DMA, so writing large amounts of data means soaking up CPU time.

poc