Performance monitoring?

[Michael O'Donnell]

>Does anyone know of any utilities which can dig into disk drive 
>performance?  I'm looking to discover the "disk busy" time, i.e., 
>what percentage of time is the disk off doing something, such that 
>requests to the disk are blocked.


I'm not sure I understand what you're trying to
measure, but note that you might find it difficult
to characterize certain behaviors of your disk units
if they have caches (pretty much all of them do)
that are enabled (pretty much all have them enabled
by default) because the caches will, to some extent,
hide the delays due to seek- and rotational-latencies.
You can always shut the caches off (using commands
like hdparm and scsiinfo) but I'm guessing that's
not representative of your normal operating mode,
so it might only serve to satisfy your curiosity
and slow the system throughput waaaaaayy down...