Difference between IDE and SCSI ??

Ben Kamen bkamen at benjammin.net
Sat Feb 2 23:23:44 UTC 2008

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 Kamen - O.D.T., S.P.
Email: bkamen AT benjammin DOT net       Web: http://www.benjammin.net
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