Les Mikesell wrote:
Ben Kamen wrote:
In the beginning, SCSI was always faster than IDE because the
intelligence of the drives (remember, IDE tends to be dumb as it's
controlled by the host), that lent the drives to be more expensive. So
think "server" and thus smarter, more expensive also demanded "faster".
Scsi needs less intervention by the main CPU but that doesn't
necessarily translate to 'faster'. The overall time is going to be
limited by the seek and transfer rate of the drive itself, which is
often identical between IDE and Scsi models. The tradeoff in cost of
putting intelligence on peripheral devices and the value of those extra
main CPU cycles (often spent waiting idly in is single-user computer
anyway) has bounced back and forth over the years. In a file server
with lots of drives, scsi is usually a big win compared to typical ide
controllers because it lets all the disks seek independently at the same
time. However even that isn't quite so simple, since specialized
controllers like the 3ware raid cards can do the same with ide drives
and also offload the work from the main CPU.
True true... the drive is ultimately a bottleneck... I should have mentioned.
but let's talk 20 years ago. I realize a lot of the technology has caught up
to today. A lot of the performance arguments these days are kinda moot.
Heck, I have 3 125GB IDE drives mounted onto my RS/6000's SCSI bus with SCSI-IDE
adapters as it was cheaper to get the adapters with drives than just large SCSI
drives. Funky.
-Ben
--
Ben Kamen - O.D.T., S.P.
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