In FreeBSD you can run "top -m io" and it will show you disk io.
What units is the WRITE/READ in, bytes or kilobytes or megabytes?
top manual page refers to the
getrusage(2) system call which generates the following block device statistics:
ru_inblockthe number of times the file system had to perform input.
ru_oublockthe number of times the file system had to perform output.
and those numbers have no unit, they seem to be event counters.