reactive data

[Gene Milligan]

* From the SCSI Reflector (scsi at symbios.com), posted by:
* Gene Milligan <Gene_Milligan at notes.seagate.com>
*
Jeffrey S. Blaalid  proposed:

>A new WRITE command (or bit in the exiting WRITE commands) that
>        marks the block as "reactive data'.  The drive shall take the
>        1 block of data, write it, and mark it as "reactive data".
>
>        The drive is free to implement this command in any convenient way,
>        provided that all subsequent reads result in a "Check Condition"
>        with a new ASC/ASCQ pointing to the block that contains the
>        "reactive data" that was earlier written.

 Assuming the new write command was going forward the generalization at first 
looks good. But it has an implied requirement which could be one of two ways:

 a) The reactive data is not valid - OK.
 b) The reactive data is valid and retrievable - May not be OK.

 Jeffrey has presumed logical blocks have headers. This assumption is not 
universally valid. It could still be OK if the frequency of the reactive marks 
are very low and the system is willing to have the marked blocks subtract from 
the allowable deallocations.

Gene
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