Re: sector CRC

From: Tim Walberg (twalbergat_private)
Date: Fri Aug 24 2001 - 13:04:27 PDT

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    On 08/23/2001 20:21 -0400, Mellen, Christopher wrote:
    >>	
    >>	 If I understand it correctly the CRC at the end of the data area of a
    >>	sector is generated when a sector is written to.  Subsequently, the CRC is
    >>	checked when the sector is read - if the CRC value doesn't match then it's
    >>	flagged as bad and some type of error should occur.
    >>	
    >>	So my question, if I use a disk utility such as diskedit and change the data
    >>	area (i.e. add a line of text to a document) in a sector.  Why then does the
    >>	sector CRC not report an error when accessing the file normally at a later
    >>	time?  or is this done with an ECC and it's correcting it on the fly as
    >>	there would be no physical issues with the sector...?
    
    Because the CRC you are referring to is generated by the hard-/firm-ware on
    the drive/controller itself. Hence when you edit a sector and write it back
    out, the CRC gets regenerated properly.
    
    					tw
    
    -- 
    twalbergat_private
    
    
    



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