hard disk problem

[DavidB]

Hmmm,

Hey, Lowell could you please read the thread I reference and give your 
opinion of the issue about the WD diagnostic tool.

So I was studying what you were talking about bad block remapping, 
dynamic bad block remapping, or western digital's term "Auto Defect 
Retirement"

I had expected that I disk would when failing to write to a bad area on 
disk and fails to mark it bad and redirect it to somewhere else on the 
disk. But reads I would not have expected the hardware to do anything 
other than give a failure. It seems there is some mechanism to do this 
automatically within the hardware with reads also.  But it seems very 
vague on how and when this is tripped. Most of my reading including one 
thing from someone who works for Maxtor is that the bad block is marked 
bad at the failed read (or succesive failed reads, says the Maxtor guy) 
however doesn't get remapped until the next write, and from my reading, 
seems to be, not until the next write to that particular sector.  So the 
bad block being read would be there until you did something to cause the 
hardware to remap it.  It doesn't seem it is done so it is totally 
hidden from view or seeing issues with bad blocks.

The system seems to be setup in order to catch problems and remap them 
at the earliest time so that the data is not totally unreachable[lost] 
the hardware will try using multiple reads with ECC to read out the 
effected data [from what I have read] and writes it somewhere else.

So again I say that the disk PROBABLY is NOT in for a soon demise.
Running the disk diagnostic tools from the disk manufacturer will remap 
the bad block immeadiately as well as other things, rather than waiting 
until you happen to write to that sector again.

This is my summation of the matter, based on reading various and sundry 
things concerning this with none giving an absolute or concrete 
answer[particularly concerning what happens with data already written to 
disk].

Sincerly,
David

Lowell Gilbert wrote:
> DavidB <odyseus00 at whatistruth.net> writes:
> 
> 
>>you probably have a couple bad blocks on the harddrive, which happens
>>over time, you need to scan and repair the harddrive.  If the bad
>>blocks reappear rather frequently then you know that the disk will
>>fail in the near future.
> 
> 
> Correct.  Assuming the hard disk was built in the 1980s.  If it's more
> recent, then it almost certainly does internal bad-block remapping on
> its own.  That means that if bad blocks are becoming visible to the
> operating system, the disk has hundreds or thousands of bad sectors,
> and is on its way to the grave.  
> 
> This would be more serious if the errors were occurring on writes
> rather than reads, but there has already been data lost, and some of
> the data on the disk is known to be corrupted.
> 
> If the original poster has a hard disk that predates the 486 chip,
> then I apologize for having given a possibly incorrect answer.  
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