Comparing methods for recording I/O – V$SYSSTAT vs HP Measureware

I wrote last year about Graphing I/O data using gnuplot and Oracle V$SYSSTAT, using a script from Kevin Closson in his article How To Produce Raw, Spreadsheet-Ready Physical I/O Data With PL/SQL. Good For Exadata, Good For Traditional Storage.
Here I’ve got a simple comparison of the data recorded through this script (in essence, Oracle’s V$SYSSTAT), and directly on the OS through HP’s MeasureWare. It’s graphed out with my new favourite tool, rrdtool:

Happily for me, the data marries up almost exactly. One might say that so it ought. But it’s always good to have explicit proof of such a supposition.