Path: utzoo!utgpu!water!watmath!clyde!mcdchg!ddsw1!karl
From: karl@ddsw1.UUCP (Karl Denninger)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Hard disk problem
Summary: No, they use an _analog_ test process.
Message-ID: <1628@ddsw1.UUCP>
Date: 2 Sep 88 14:32:33 GMT
References: <20173@tut.cis.ohio-state.edu> <360@pigs.UUCP> <9971@eddie.MIT.EDU> <12193@iuvax.cs.indiana.edu> <6887@bloom-beacon.MIT.EDU>
Reply-To: karl@ddsw1.UUCP (Karl Denninger)
Organization: Macro Computer Solutions, Inc., Mundelein, IL
Lines: 30

In article <6887@bloom-beacon.MIT.EDU> arwall@athena.mit.edu (Anders R Wallgren) writes:
>In article <12193@iuvax.cs.indiana.edu>, bobmon@iuvax (RAMontante) writes:
>>A low-level format will search for and avoid bad areas on the hard
>>disk.  The value of the manufacturer's list is that it was generated by
>>rigorous testing that may have caught defects the formatter would
>>miss.  It may also save some time, since the formatter needn't test
>>those areas.
>
>Can somebody verify this?  It's been intimated to me by a friend in
>the business that the 'rigorous' testing is nothing more than a
>low-level format.

The "rigorous test" is normally done on analog equipment, and does indeed
catch errors that aren't otherwise apparent.   You can only get a "go/nogo"
indication from a digital signal -- but analog equipment can give you a
_value_ which is open to interpretation as ok, marginal, or bad.

Note that some of the "defects" on your drive may be _between_ sectors (ie:
in the dead space between the end of a sector and the ID mark for the next
one).  These could _never_ be found by a low level format, since you don't
even read/write there in normal operation!

As verification, we've used media analysis programs to validate drives
before (those that take 48 hours to complete!) -- they almost never catch all 
of the errors that are on the label, usually due to the error(s) falling
between sectors.

--
Karl Denninger (ddsw1!karl) Data: (312) 566-8912, Voice: (312) 566-8910
Macro Computer Solutions, Inc.    "Quality solutions at a fair price"