I have been looking for a while for a special tool which displays the progress done by a process.
I eventually found the right program to do that job : pv
To install it :
root@localhost:~# apt-get install pv
To test it, here is an example to see how fast your computer reads from /dev/zero :
fool@localhost:~$ pv /dev/zero > /dev/null
228GO 0:03:08 [1,43GO/s] [ <=> ]
More information about its options : man pv