Btrfs devel - Jan 2014 - RFE: proactive "marginally bad" block detection during scrubs

Most consumer drives have bad sector timeouts that aren't configurable, and
are in the ~120 second realm. The kernel puts a SCSI command timer on each
command, which by default is 30 seconds. This mismatch means drives can develop
bad sectors that can't be recovered, because the kernel resets the device
before the drive gives up and reports a media error along with the affected LBA.

Would it be possible for Btrfs scrubs to put a timer on each LBA read request,
and if there's a delay, overwrite the delayed LBAs? That way latent sector
errors won't get so bad that they take more than 30 seconds to recover.
Overwriting slow sectors should fix the problem.

Yes? No? Other?


Chris Murphy--
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