What causes a bad block in a hard drive?

soulfly9_2

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May 19, 2014
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Title says it all..

How do bad blocks occur in hard drives?


I tried to fix my brother seagate external by taking the read/write head off the platter and putting it back in starting position like a few youtube videos instructed, thinking that might resolve the problem of the drive not being read. But no, even viewer told me it was a bad block in the drive.

I did a bit of research, but nothing tells me actually how they occur? Can anyone help? What causes a bad block in a drive?
 
Solution
media failure due to microscopic manufacturing defect, ageing, or wear and tear. In other words, <mod edit> happens. Usually manufacturers expect it and there are spare blocks and mechanisms to reallocate or mark as bad so the operation of the unit is not impacted by limited numbers of failures.

Bear in mind a hard drive is not supposed to last indefinitely.

But if you're disassembling a hard drive and reassembling components that usually gets assembeld in a clean room, I shouldn't have to tell you anything, you know more than I do. :)

<Mod Note: Let's watch our language in the forums>
media failure due to microscopic manufacturing defect, ageing, or wear and tear. In other words, <mod edit> happens. Usually manufacturers expect it and there are spare blocks and mechanisms to reallocate or mark as bad so the operation of the unit is not impacted by limited numbers of failures.

Bear in mind a hard drive is not supposed to last indefinitely.

But if you're disassembling a hard drive and reassembling components that usually gets assembeld in a clean room, I shouldn't have to tell you anything, you know more than I do. :)

<Mod Note: Let's watch our language in the forums>
 
Solution


If the head ever touch the platter surface, it's called a head crash and it's unrecoverable. Bad sectors are due to media failures or errors, and alternate blocks/sectors can be allocated by design. A head crash is irrecoverable and catastrophic.

I don't know how come people seem unable to Google or research their answers better. :(

Head crash: http://en.wikipedia.org/wiki/Head_crash

Bad sector: http://en.wikipedia.org/wiki/Bad_sector

 

Yuna

Honorable
Dec 18, 2012
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Oh I am so so so so so so so so so so very very sorry it seems that I had provided a catastrophic mis-information. All of what I shared is the pandora's box equivalent of; you(yuna) you are a retarded imbecile, you should be ashamed of sharing such utter nonsense immature rubbish, as a result your(yuna) mere existence has fouled, corrupted, tainted and ruined this once pristine home many call earth. You(yuna) should be banished to the very depths of hell serving as fire mat(a luxury indeed) for the hell king itself for, eternity is not even worth mentioning. Yuna's statement: I am very sorry for providing rubbish information that could result in the death of many many lives, the information I provided has blinded God himself as being something so unholy(words can't describe). I have nothing(deserves absolutely nothing) to say, I am ashamed for my words so so very ashamed. :(