Some of my favorate Linux tools at work:

(1) use `watch -d` whenever you want to monitor the change of some shell commands' output, i.e. use the following command to monitor the disk-sizes:

 

(2) `sar -d`: used to monitor the disk read/write

 

Pay attention to the following fields: rd_sec/s, wr_sec/s, await, %util. small await and %util tends to be good. [%util below %10 is a sign of in-memory I/O]

(3) top: after entering the `top` interface, press 'c', 'b', 'x', '1'(if you have multiple CPUs). your `top` screen will be very 'active' when your shell is running multi-process programs. you can split the resulting windows by using 'A', 'G', '-'.. read the man page..