I have a WD6400AAKS-75A7B0 disk. The short SMART test fails with a 0x79 code. HDS Overview says "The drive found 1 bad sector during its self-test. There is 1 weak sector found on the disk surface. It may be remapped any time in the later use of the disk". So, I run the data refresh test (read-write-read) and it does indeed find a bad sector (Error 23: CRC data error). This all makes sense to me. The part that doesn't make sense is that when I run the test again, it finds the same bad sector.
Why hasn't the disk reallocated it at this point? This keeps tools like Clonezilla from running, unless I use rescue mode (ignore errors and continue).
Is the data in this sector lost at this point?
When the disk does reallocate the sector, will it copy the data from the old sector to the new one even though it knows that the old one is bad?
TIA
Cannot get weak sector to be marked as bad
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hdsentinel
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Re: Cannot get weak sector to be marked as bad
> The part that doesn't make sense is that when I run the test again, it finds the same bad sector.
Excuse me for the confusion, but this is somehow expected now.
The data refresh test (read-write-read) test (depending on the issue) may NOT fix the currently reported weak sector, as the test performs the write operation only to the sectors which can be read.
As that particular sector can't be read at all, no write operation (so no repair) done, exactly to allow the opportunity to perform different way for testing, for example to connect the hard disk differently (eg. by external USB adapter if now connected internally - or vice versa) or trying to recover the data in an other computer.
Please check: http://www.hdsentinel.com/hard_disk_cas ... ectors.php
which describes that the best way to repair weak sectors is to perform overwrite of the particular sector, for example by the Disk menu -> Surface test -> Reinitialise disk surface test.
Working on other, quicker and easier solution as well - just due to restrictions of newer Windows OSes, things may be harder.
> When the disk does reallocate the sector, will it copy the data from the old sector to the new one even though it knows that the old one is bad?
When the disk really reallocates the sector then yes, it tries to recover the data from the old sector and move to the spare area, this is called reallocation. Then it re-directs all further reads/writes to this spare area.
The problem is that in many cases this reallocation can't be completed easily - and the data may be damaged (if it could be read without problems then the original sector would not show errors). So yes, that particular sector may be damaged.
However, for weak sectors, the situation is different: in almost all cases weak sectors are not really related to physical damage, but may be related to an error occured during write, for example incomplete operation due to power loss, power failure and so.
Then the weak sector is not accessible (for reading) but after overwrite, the hard disk fixes it: either by performing the reallocation (if really required) or just return the status of the weak sector to normal, if it's confirmed that the sector is usable.
Excuse me for the confusion, but this is somehow expected now.
The data refresh test (read-write-read) test (depending on the issue) may NOT fix the currently reported weak sector, as the test performs the write operation only to the sectors which can be read.
As that particular sector can't be read at all, no write operation (so no repair) done, exactly to allow the opportunity to perform different way for testing, for example to connect the hard disk differently (eg. by external USB adapter if now connected internally - or vice versa) or trying to recover the data in an other computer.
Please check: http://www.hdsentinel.com/hard_disk_cas ... ectors.php
which describes that the best way to repair weak sectors is to perform overwrite of the particular sector, for example by the Disk menu -> Surface test -> Reinitialise disk surface test.
Working on other, quicker and easier solution as well - just due to restrictions of newer Windows OSes, things may be harder.
> When the disk does reallocate the sector, will it copy the data from the old sector to the new one even though it knows that the old one is bad?
When the disk really reallocates the sector then yes, it tries to recover the data from the old sector and move to the spare area, this is called reallocation. Then it re-directs all further reads/writes to this spare area.
The problem is that in many cases this reallocation can't be completed easily - and the data may be damaged (if it could be read without problems then the original sector would not show errors). So yes, that particular sector may be damaged.
However, for weak sectors, the situation is different: in almost all cases weak sectors are not really related to physical damage, but may be related to an error occured during write, for example incomplete operation due to power loss, power failure and so.
Then the weak sector is not accessible (for reading) but after overwrite, the hard disk fixes it: either by performing the reallocation (if really required) or just return the status of the weak sector to normal, if it's confirmed that the sector is usable.
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sewerurchin
- Posts: 2
- Joined: 2014.06.05. 17:06
Re: Cannot get weak sector to be marked as bad
Thank you for your reply. I hadn't considered the fact that having the read fail would keep it from performing the write. So, in this case, I didn't understand why a re-initialize would fix it but a refresh wouldn't. Thanks for helping me understand.