Hi there,
Couple of interesting points to make here. SCSI is and maybe
always will be faster, its driven by the server industry and consequently
performance and robustness are its primary concerns/design criteria. You
can't get platter speeds in DIE drives beyond 7200 rpm that I have seen,
while scsi drives are already at 15000 rpm this alone gives an enormous
performance enhancement -- latency and sustained transfer rate. Along with
this, as has been identified, on a single IRQ on an Intel box you can have a
dual channel controller communicating with 30 scsi devices. A single IRQ is
needed for each channel on a standard dual channel DIE controller, so for
each 2 DIE devices you loose one IRQ. This gets messy really quickly on an
Intel box with its limited number of available IRQs..
Of the scsi flavours out there ultra 160 and 320 offer
transfer rates of 160 or 320 Mb/sec and fibre channel which is a serial
implementation of the scsi command protocol offers transfer rates of 200
MB/sec {correct me if I have the mega bits bytes thing wrong}. IDE offers a
max currently of 100 Mb/sec. With IDE raid on the increase in personal
motherboards {ala ABIT and co} you can get some pretty hefty performance for
very minimal outlay of cash, however if money is not a limiting factor or
you're going to be doing large transaction processing or server class work
then scsi is the way to go.
Part of the SCSI advantage is the SCSI controller. It has a
'cpu' of sorts on the card which handles all the fetch and carrying and
talking to the devices, this can alleviate a significant load on a busy
machine. Your CPU says 'get me file x' and then goes back to what its
doing...and the scsi controller says 'oi that stuff is availlable now'.
IDE is totally managed by your cpu and this can make for a
machine that pauses a lot when doing stuff. It really pisses me using an IDE
machine as I have always had scsi machines and find it frustrating have to
pause while my machine swaps to files or whatever.
It really does depend on the application you have in mind, not to mention
you budget.
Regards
D.
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