Changes between Version 10 and Version 11 of FAQ


Ignore:
Timestamp:
Sep 26, 2009, 5:49:49 PM (10 years ago)
Author:
Gabriele Pohl
Comment:

Transform HTML to Wiki-Syntax

Legend:

Unmodified
Added
Removed
Modified
  • FAQ

    v10 v11  
    311311----
    312312
     313=== {{{smartd}}} is warning that my ATA disk has unreadable or uncorrectable or pending sectors. What's going on? ===
     314
     315Disk drives store data in blocks (sectors) of 512 bytes.  Each 512 bytes has additional bytes appended to it (usually 40 to 60) which are used internally by the disk firmware for error checking/detection and correction.  These are called ECC bytes.
     316
     317Sometimes the data in a sector gets corrupted.  This can happen because a speck of dust scratched the disk, or because the disk was powered down while writing data to that sector, or for other reasons. Usually the ECC bytes can be used to correct the corrupted data. However if the ECC bytes are inconsistent or can't be used to correct the bad data, then the 512 bytes of data are lost.  Such a sector is called unreadable or uncorrectable.
     318
     319If your disk has an unreadable sector, this means that some of your data can't be retrieved.  You can force the disk to replace the unreadable sector with a spare good sector, but only at the price of losing the 512 bytes of data forever.
     320
     321Disks with uncorrectable sectors can often be repaired by using the disk manufaturer's 'disk evaluation and repair' utility (see previous FAQ entry).  Beware: this may force reallocation of the lost sector and thus corrupt or destroy any file system on the disk. See [http://smartmontools.sourceforge.net/badblockhowto.html Bad block HOWTO] for generic Linux instructions.
     322
     323Normally when an uncorrectable sector is found, the disk puts this onto a 'pending sector list' to indicate that it should be replaced with a spare good sector.  However this replacement won't take place until either the disk can read the data on the bad sector, or is commanded to write new data to that bad sector.
     324
     325----
     326
    313327=== Where can I find manufacturer-specific disk-testing utilities? ===
    314328
     
    473487#!html
    474488
    475 
    476 <!-- corrupt sectors -->
    477 <h3><a name="corrupt-sectors"></a><tt>smartd</tt> is warning that my ATA disk has unreadable or uncorrectable or pending sectors. What's going on?</h3>
    478 
    479 <p>
    480 Disk drives store data in blocks (sectors) of 512 bytes.  Each 512
    481 bytes has additional bytes appended to it (usually 40 to 60) which are
    482 used internally by the disk firmware for error checking/detection and
    483 correction.  These are called ECC bytes.
    484 </p>
    485 <p>
    486 Sometimes the data in a sector gets corrupted.  This can happen
    487 because a speck of dust scratched the disk, or because the disk was
    488 powered down while writing data to that sector, or for other reasons.
    489 Usually the ECC bytes can be used to correct the corrupted data.
    490 However if the ECC bytes are inconsistent or can't be used to correct
    491 the bad data, then the 512 bytes of data are lost.  Such a sector is
    492 called unreadable or uncorrectable.
    493 </p>
    494 <p>
    495 If your disk has an unreadable sector, this means that some of your
    496 data can't be retrieved.  You can force the disk to replace the
    497 unreadable sector with a spare good sector, but only at the price of
    498 losing the 512 bytes of data forever.
    499 </p>
    500 
    501 <p>
    502 Disks with uncorrectable sectors can often be repaired by using the
    503 disk manufaturer's 'disk evaluation and repair' utility (see previous
    504 FAQ entry).  Beware: this may force reallocation of the lost sector
    505 and thus corrupt or destroy any file system on the disk. See <a
    506 href="badblockhowto.html">Bad block HOWTO</a>
    507 for generic Linux instructions.
    508 </p>
    509 <p>
    510 Normally when an uncorrectable sector is found, the disk puts this
    511 onto a 'pending sector list' to indicate that it should be replaced
    512 with a spare good sector.  However this replacement won't take place
    513 until either the disk can read the data on the bad sector, or is
    514 commanded to write new data to that bad sector.
    515 </p>
    516 <hr />
    517 
    518489<h3><a name="bios-setting"></a>My computer's BIOS has a SMART enable/disable setting.  What
    519490does it do, and how should I set it?</h3>