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From: cdold@starfish.Convergent.COM (Clarence Dold)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Spinrite Concerns
Message-ID: <663@starfish.Convergent.COM>
Date: 24 Aug 88 23:17:12 GMT
References: <329@octopus.UUCP>
Organization: Convergent Technologies, San Jose, CA
Lines: 32

From article <329@octopus.UUCP>, by pete@octopus.UUCP (Pete Holzmann):
> 	2) Actual surface defects on the disk will be found by the SpinRite
> 		thorough testing. It is a more intense test than drive
> 		manufacturers use for the most part!
Whoa, there!
Disk Manufacturers can and generally do perform two types of test that you
could never touch in the field:
	1) Analog testing, to check for physical dropouts.  This doesn't
	even use drive electronics, I don't see how you could duplicate it.
	2) Reduced margin testing.  Lower the write current during pattern
	generation, reduce read gain during pattern checking.
Both of these methods yield reported defects that you will **NEVER** catch
regardless of how clever your techniques might be.  The only way you might
see them is through media aging, which is what they are trying to predict.
What you will catch are solid defects.  Listen very carefully while
doing the format.  WD1010-001 chips would perform four retries before
reporting a 'soft' error.

Give up the badspots.  Don't play games with the future of your data.
Particularly, watch for bad spots mapped on the same head, same sector,
on adjacent tracks.  Radial Striation is a common defect.

> 	3) On a new drive, there's a defect list. DOS just wipes out the
> 		whole track in all cases, even though there's a high
> 		probability that the actual defect is located where it
> 		won't cause any interference with data on the track. SpinRite
> 		tests the track to see if this is the case. If the defect
> 		will not interfere, it returns the track to good use. This
> 		is not 'marginal'. 
There might be defects with Byte From Index greater than ~9500 that won't
affect data.  There are also some 'gaps' in disk data where you could
ignore defects.  If SpinRite CALCULATES these places, that would be great,
but just field testing doesn't cut it.