[NCLUG] badblocks and smartctl?

[Zak Smith]

On Mon, May 26, 2014 at 06:54:56AM -0600, John Gilmore wrote:
> So there are no bad blocks? Maybe it was corrected? So below find the
> output from smartctl -a, which *still* shows an uncorrectable sector
> (not that the raw_value of "Current_Pending_Sector" and
> "Offline_Uncorrectable" is 1)
>
> Also note that the error log says "UNC at LBA = 0x0fffffff =
> 268435455" which *is* in the range that badblocks scanned. I'd go
> ahead with the assumption that it's accurate, and use dd to touch that
> sector (I'm using zfs with a mirror, so I can just scrub and any
> corruption will be corrected afterwards, I don't have to worry about
> damaging my data)
>
> However, I'm concerned about doing that because "0x0fffffff" is just
> such a nice round number that I suspect it's inaccurate, or that

Searching for "UNC at LBA = 0x0fffffff" reports MANY people getting
this exact same value over a variety of drive types and sizes, so I
suspect this is a default value in a class of error conditions.  It is
almost certainly not the real sector/LBA.

smartctl (8) says this,

   If the command that caused the error was a READ or WRITE command,
   then the Logical Block Address (LBA) at which the error occurred
   will be printed in base 10 and base 16.  The LBA is a linear
   address, which counts 512-byte sectors on the disk, starting from
   zero.  (Because of the limitations of the SMART error log, if the
   LBA is greater than 0xfffffff, then either no error log entry will
   be made, or the error log entry will have an incorrect LBA. This
   may happen for drives with a capacity greater than 128 GiB or 137
   GB.) On Linux systems the smartmontools web page has instructions
   about how to convert the LBA address to the name of the disk file
   containing the erroneous disk sector.

Smartctl has a more in-depth self test, I believe.

Another thing I would check is if there are any messages in syslog
about sda errors.






--
# Zak Smith    mobile 970-232-4468