[ale] read after write verify?, data scrubbing procedures

[Erik Mathis]

Ron, this might be of some interest to you from our overlords at google

http://tinyurl.com/95xdrwv

On 10/25/2012 04:43 PM, Ron Frazier (ALE) wrote:
> Hi all,
>
> In another thread, I mentioned that I do a manual data scrubbing procedure on my hard drives which involves reading inverting writing reading inverting writing all sectors on the hard drive periodically with Spinrite.  As an alternative, I use the Linux badblocks non destructive read write mode.  This process is certainly effective in reverifying the integrity of the drive barring any mechanical problems or controller problems.  As also mentioned in another thread, once some drives develop bad sectors, and based partly on advice here, I replace them.
>
> I basically want to have as much evidence as I can that the drive is reliable, periodically, still understanding that spontaneous or semi spontaneous failures are possible.
>
> I am considering methods of reducing the maintenance procedures while still maintaining high confidence in the drives.  Mike T mentioned some automation and raid procedures that I may be able to implement on some machines at a future date.  In the mean time, I'm considering altering my procedures without giving up too much functionality.
>
> My first question is, does a HDD do a read after write verify by default?  So, if the application or OS sends a command to write a sector, will a verify operation automatically be done after the write process, and, if the write failed, will the data be automatically relocated to a spare sector?  I'm assuming that this is the case, but would like to verify that.
>
> Assuming the read after write verify happens, then, if I write data to every sector of a drive during a backup operation, as I mentioned in the clonezilla thread, then, effectively, I have written and read every sector on the target drive.  Perhaps, then, a successful backup operation can take the place of my data scrubbing activity on the target drive.
>
> Then, there is the question of the data scrubbing on the source drive.  In this case, once I've completed a backup, I will have read each sector on the source drive.  Assuming there are no read errors,  (If there were, I have to get out the big guns.)  then, this has accomplished 1/2 of what my scrubbing does, the read half.
>
> So, the question arises as to what about the write test part of my scrubbing operation for the source drive, which didn't get done.  Normally, my scrubbing operation would have written to each sector.  If the drive automatically detects write problems when a write is attempted, perhaps the write scrubbing operation is not necessary, or is less necessary.
>
> Hope this makes any sense whatsoever.  Any opinions?
>
> Thanks in advance.
>
> Sincerely,
>
> Ron
>
>
>
> --
>
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>
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> Ron Frazier
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