Measuring I/O in 2.6 and the tools you'll need

A lot depends on what you are trying to do, and the amount of information that you need to capture and in what format. Why don't you start with iostat and see how that works for you? This command monitors system I/O device loading by observing the time devices that are active in relation to their average transfer rates. It is an interactive tool that can also generate reports that can be used to modify your system configuration to better balance your I/O load between your disks and adapter.

If you want some fancy graphs to help you keep historic data and also something that you can export to Excel spreadsheets,...

try to pick up a copy of nmon for Linux. It is a fabulous tool that can give you much more than I/O, but captures I/O info as well. Good luck!