Changes between Version 9 and Version 10 of FAQ


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Timestamp:
Sep 26, 2009, 5:36:29 PM (10 years ago)
Author:
Gabriele Pohl
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Transform HTML to Wiki-Syntax

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  • FAQ

    v9 v10  
    288288----
    289289
     290=== ATA drive is failing self-tests, but SMART health status is 'PASSED'. What's going on? ===
     291
     292If your ATA drive supports self-tests, you should run them on a regular basis, for example one per week:
     293{{{
     294 smartctl -t long /dev/hd?
     295}}}
     296
     297After the test has completed, you should examine the results with:
     298{{{
     299 smartctl -l selftest /dev/hd?
     300}}}
     301
     302If the drive fails a self-test, but still has '{{{PASSED}}}' SMART health status, this usually means that there is a corrupted (uncorrectable=UNC) sector on the disk. This means that the ECC data stored at that sector is not consistent with the user data stored at that sector, and an attempt to read the sector fails with a UNC error. This can be a one-time transient effect: a sudden power failure while the disk was writing to the sector corrupted the ECC code or data, but the sector <em>could</em> correctly store new data. Or it can be a permanent effect: the magnetic media has been damaged by a bit of dust, and the sector could ''not'' correctly store new data.
     303
     304If the disk can read the sector of data a single time, and the damage is permanent, not transient, then the disk firmware will mark the sector as 'bad' and allocate a spare sector to replace it.  But if the disk can't read the sector even once, then it won't reallocate the sector, in hopes of being able, at some time in the future, to read the data from it.  '''A write to an unreadable (corrupted) sector will fix the problem.''' If the damage is transient, then new consistent data will be written to the sector.
     305If the damange is permanent, then the write will force sector reallocation. Please see [http://smartmontools.sourceforge.net/badblockhowto.html Bad block HOWTO] for instructions about how to force this sector to reallocate (Linux only).
     306
     307The disk still has passing health status because the firmware has not found other signs of trouble, such as a failing servo.
     308
     309Such disks can often be repaired by using the disk manufaturer's 'disk evaluation and repair' utility.  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.
     310
     311----
     312
    290313=== Where can I find manufacturer-specific disk-testing utilities? ===
    291314
     
    450473#!html
    451474
    452 
    453 
    454 
    455 
    456 <!-- Selftest failed but status is 'PASS' -->
    457 <h3><a name="selftest-failed"></a>My ATA drive is failing its self-tests, but its SMART health status is 'PASS'. What's going on?</h3>
    458 
    459 <p>If your ATA drive supports self-tests, you should run them on a
    460 regular basis, for example one per week:
    461 <br/><span class="code">smartctl -t long /dev/hd?</span><br/>
    462 After the test has completed, you should examine the results with:
    463 <br/><span class="code">smartctl -l selftest /dev/hd?</span></p>
    464 
    465 <p>If the drive fails a self-test, but still has '<tt>PASS</tt>' SMART health
    466 status, this usually means that there is a corrupted (uncorrectable=UNC) sector on the
    467 disk. This means that the ECC data stored at that sector is not
    468 consistent with the user data stored at that sector, and an attempt to read the sector fails with a UNC error.
    469 This can be a one-time transient effect: a sudden power failure
    470 while the disk was writing to the sector corrupted the
    471 ECC code or data, but the sector <em>could</em> correctly store new data.
    472 Or it can be a permanent effect: the magnetic media
    473 has been damaged by a bit of dust, and the sector could <em>not</em> correctly store new data.</p>
    474 
    475 <p>If the disk can read the
    476 sector of data a single time, and the damage is permanent, not transient, then the disk firmware will mark the
    477 sector as 'bad' and allocate a spare sector to replace it.  But
    478 if the disk can't read the sector even once, then it won't reallocate
    479 the sector, in hopes of being able, at some time in the future, to
    480 read the data from it.  <b>A write to an unreadable (corrupted) sector will fix the problem.</b>
    481 If the damage is transient, then new consistent data will be written to the sector.
    482 If the damange is permanent, then the write will force sector reallocation.
    483 Please see <a
    484 href="badblockhowto.html" target="_blank">Bad block HOWTO</a>
    485 for instructions about how to force this sector to reallocate (Linux only).</p>
    486 
    487 <p>The disk still has passing health status because the firmware has not
    488 found other signs of trouble, such as a failing servo.</p>
    489 
    490 <p>Such disks can often be repaired by using the disk manufaturer's 'disk
    491 evaluation and repair' utility.  Beware: this may force reallocation
    492 of the lost sector and thus corrupt or destroy any file system on the
    493 disk. See <a
    494 href="badblockhowto.html" target="_blank">Bad block HOWTO</a>
    495 for generic Linux instructions.</p>
    496 
    497 <hr />
    498475
    499476<!-- corrupt sectors -->