>> so what is the exact problem with IDE?
> See http://www.hardwarecentral.com/hardwarecentral/tutorials/43/1/
... which, after reading it, wasn't the link I meant to send.
I've used IDE and SCSI systems extensively over the past few years,
and they both have merits. Chief among IDE's merits is cost of
purchase; the mass-market economics of the controllers and drives have
really driven costs down.
However, cost of purchase isn't the only cost associated with a
system - my experience of IDE is "it's only cheaper if your time is
free". Modern SCSI systems "just work", and you don't have to waste
time messing around and worrying about whether DMA is on, or which
transfer mode your controller is in.
Also, you can have up to sixteen devices per SCSI bus, including the
controller. Big win if you want to do RAID and whatnot.
Unlike IDE, the slowest device on the bus doesn't hamper the whole
Unlike IDE, more than one device can be active at a time. Transfers
between devices need not involve the controller at all.
Unlike IDE, devices can be dynamically added and removed.
Unlike IDE, commands can be queued up at the controller and the CPU
need not become involved until they're all finished.
In a situation where you have both a large data flow *and* intense CPU
activity (eg : a big compile), SCSI really wins - the constant
mode-switching which the CPU has to do to cope with IDE really hits
performance. Example, my machine ogma (fairly modest PIII/500) takes
about fifteen minutes to compile the kernel on its EIDE drive (ATA66,
DMA enabled), but only eleven on its SCSI drive.
Basically, people who go on and on about how SCSI is better are
sometimes just snobs repeating what they've been told, but at other
times (like this), they're speaking from real experience. I wouldn't
use IDE on a machine where disk I/O or ongoing maintenance was going
to be anything other than an trifle.
Colm Buckley @ NewWorld Commerce
Business: +353 1 4334334 / colm at nwcgroup.com / http://www.nwcgroup.com/
Personal: +353 87 2469146 / colm at tuatha.org / http://www.tuatha.org/~colm/
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