capture an "I/O trace" on one machine, then replay the same "I/O trace" upon another machine (i.e., use the I/O trace as "input" and actually perform the same I/O operations in the same sequence upon another machine)?
yup. but that may be unnecessary. not sure if that could be done with this. but setting up some sort of batch file to initiate programs in the same sequence (possibly with some time intervals between) could be just as effective. the main goal is to be able to compare the two systems' I/O performance under identical load patterns.