ddrescue. It will continue after errors, where
dd will simply fail.
ddrescue is in the repos. On 13.04, I typed
sudo apt-get install gddrescue
sudo fdisk -l or
dmesg to figure out the device location eg:
/dev/sdb, then run a command such as
ddrescue /dev/sdb /home/user/desktop/bkp.img
there are many options to
ddrescue, and you may want to read the
man pages. Also I'm not sure why your hardware is failing, and dumping
dd. One bad block could make
dd quit, but so could intermittent power failures.
dmesg may tell you more about hardware failures you may be experiencing.
MAKE SURE the device is not mounted! when you try to do data recovery, imaging, etc. This may cause problems.
There is a lot of things that can go wrong in data recovery. Post back if you have problems.
testdisk is a nice utility for doing data recovery once you have an image.
Just for clarity, is this a usb hard drive or usb (solid state memory) device?
I/O errors are typically indicative of hardware malfunctions rather than file-system corruptions.
Also try obtaining the SMART data analysis of the device, if it is available. This may tell you things like if the device his been over heating, powered on for a long time, has bad sectors, exposed to more than X no. of Gs etc.