Hi, This is a follow-up to the thread "Hard Disk Failing."
To recap, SMART reported drive errors of the "...XYZ..." variety on a young and lightly used Western Digital Raptor drive. It turned out (see below) that any attempt to access any of sectors 261200 through 261343 (a 144-sector range) would trigger retries that ultimately failed. SMART self-tests likewise failed upon reaching the first of these sectors. Reading some articles on SMART by Bruce Allen (the author of the smartmontools package) suggested that these errors can sometimes be caused by mere discrepancy between the ECC data and the 512 bytes of actual recorded content of a given sector and that there could be many causes for this, including power failures while writing. I decided to try a simple experiment: I would determine all the sectors that elicited an error when they were read and then rewrite them. I did this by using the "dd_rescue" utility. One of its options (-o) records a list of blocks for which unrecoverable errors were reported by the OS. This is how I obtained the list of 144 sectors that showed read errors. Note: dd_rescue is apparently not designed to write to /dev/null, and every write operation it attempts to /dev/null yields an error message. Once I had the list of (supposedly) bad blocks, I simply used an invocation of "dd" (the stock dd, not dd_rescue) to copy zero bytes (supplied by /dev/zero, of course) over the failing sectors. Voila! After this, the bad sectors could be read without eliciting any error indication at all, requiring no retries nor producing any kernel messages. The moral: Don't give up easily if you have a young, expensive drive that starts to give you SMART errors! An interesting aside: The actual capacity of this drive appears to be nearly 7 GB (out of just under 140 GB) _larger_ than specified. Randall Schulz -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
