Iotop

iotop is a top-like utility that monitors system input/output.

Kernel
The CONFIG_TASK_IO_ACCOUNTING variable must be enabled in the Linux kernel for the command to work properly. It can be found at this location:

Emerge
Install the package:

External resources

 * iotop on Freecode.com
 * iotop's man page ( man iotop )
 * Slicehost article on iotop