HDTach-like block device benchmarking script for Linux/UNIX. blkdevbench measures sequential read performance of a block device vs. position on the device and displays a plot just like HDTach.
sarface is a user-interface to the sysstat/sar database which inputs data from sar and plots to a live X11 graph via gnuplot. It mimics the cmd-line options from sar but can cross-plot any two or more stats and apply simple mathematical functions them.