iotop

I highly recommend anyone that want to know what is writing to the devices of your linux machine get a program called iotop

Linux has always been able to show how much I/O was going on (the bi and bo columns of the vmstat 1 command).

Iotop is a Python program with a top like UI used to show of behalf of which process is the I/O going on. > It requires Python ≥ 2.7 and a Linux kernel ≥ 2.6.20 with the TASK_DELAY_ACCT CONFIG_TASKSTATS, TASK_IO_ACCOUNTING and CONFIG_VM_EVENT_COUNTERS options on.

http://guichaz.free.fr/iotop/

I simply installed it with

# sudo apt-get install iotop