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some ATA drives don't set their Current and/or Offline
Pending Sector Counts (backwards compatible ATA-4/SFF-8035i SMART data
Attributes) to zero, even when an extended read scan indicates that ALL
the disk sectors can be read.
Thanks for sharing.
Why is this?
I'm here hoping I can help by asking ignorant questions ...
Is it because after a sector goes onto the pending sector list, it can't be cleared from the list until it is WRITEn to, even if there is a subsequent sucessful READ of that sector?
What's a "SMART" "pending sector list"?
Is it the list of blocks for which read attempts failed?
Yes, automagically erasing those blocks could destroy data, if the unreadability was temporary e.g. due to heat, electric fields, magnetic fields, muck on the heads, etc. Yes, having failed to read once correlates well with failing to read later, even if a read in between did work. So yes, especially in the removable world where more heads are available, some people like the policy of waiting to reallocate such blocks until rewritten. Other people like to rewrite automagically after a read almost fails, rather than fails altogether, although that policy collides slightly with concepts like write-protected and write-once discs not changing.
Pat LaVarre
