Two possiblilities come to mind.  Either some program improperly wrote to a portion of that disk,
corrupting the data that is there (I think that this is unlikely).  If the program that "owned" that data
had a bug, then it, too, could have written bad data.  In both of these cases, the actual disk hardware
is still good.

A hard drive has platters with magnetic material on them.  The head that reads the magnetic material
rides over the platter at a very, very small distance.  If a speck of dust, that has been floating around
innocuously for the last year or two, suddenly gets caught in the wrong place by the head, it can rip out
a bit of the magnetic material.  Formats and disk checks can sometimes repair this problem if the dust
and chip get lodged in a harmless place.  If they do not, then, over time, the number of bad spots will
increase.  It is also possible for a piece of magnetic material, that is not stuck well, to break loose
and cause the same type of problems.  These kinds of problems were more common in the past then they are
today.

Dean Kukral


----- Original Message -----
From: Hugh Vandervoort
Sent: Friday, September 02, 2005 1:54 AM
Subject: Re: [PCBUILD] Disk IO Error


After much fiddling, I determined that one of the RAID disks had become
corrupt. (How does that happen?)

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