[ale] EIDE vs SCSI

[Stephan Uphoff]

Matthew Brown wrote:
>I use EIDE almost all the time and have seen very little actual trouble with
>it.  Is it slower?  Well, maybe, but a single user probably would not notice
>it that much unless they are really pumping data - not number-crunching! -
>actually pumping data (web serving, database work, etc.)

I agree that the performance difference should be small to nonexistent
on a single user system.

There is however a reliability difference:
 
The last time I looked SCSI drives typically had a MTBF
(Mean time between failures) between 800000 - 1000000 hours. 
IDE drives typically had a MTBF between  250000 - 300000 hours.

This translate for a linux system that runs day and night that
the probability of  getting a hard disk failure in the first year is:

	SCSI Drive:  1.1% - 0.8%
	IDE  Drive:  3.5% - 2.9%

(This might have changed in the meantime and I have also seen cheap SCSI drives
with only 500000 MTBF)

The MTBF describes the case that the whole drive is going bad 
- there are other important issues concerning read / write failures

This is a marketing issue and has nothing to do with the 
electrical/protocol/performance of IDE vs SCSI interface

Is the reliability difference worth the price - difference ?
Depends on what the drives are used for.

Stephan