[Beowulf] Big storage

Bruce Allen ballen at gravity.phys.uwm.edu
Thu Aug 30 03:25:15 PDT 2007

>> When I buy RAID controllers, I put this requirement directly in my bid
>> specifications.  I say something like the following:
>> ------------------------------------------------------------------
>> During a READ operation, if the RAID controller finds an unreadable
>> (uncorrectable) disk sector, then it will immediately reconstruct the
>> missing data for that sector using redundant data from the rest of the
>> array, and WRITE that data to the unreadable (uncorrectable) sector to
>> force sector reallocation if needed by the disk.
>> In addition, the RAID controller will perform a continous or regular
>> (at least daily) background scan of all disk sectors to identify and
>> repair any unreadable sectors as described above.
>> ------------------------------------------------------------------
> I think you should add a parity verification to this - not just a
> sector scan.

Good idea.  In other words, don't just check that all disk surfaces are 
readable by the disk device.  Also check that the data is consistent from 
the RAID perspective.  Did I understand you correctly?


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