[Maybe OT] What causes "bad blocks" to appear in disk drives

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Chaos Master

Hello people.

I have an oldish 800MB hard drive here which is still working (it stores some
audio files).

Recently, after a power surge, it developed a "bad block" (4kb marked as bad),
but it still works correctly.

Q: What is a "bad block" in a hard drive?
Physical damage?

Thanks
--
Chaos Master®, posting from Brazil. REPLY TO GROUP!
"People told me I can't dress like a fairy.
I say, I'm in a rock band and I can do what the hell I want!"
-- Amy Lee

Note: please don't give me TinyURL addresses.
 
Hi!
Recently, after a power surge, it developed a "bad block" (4kb marked as bad),
but it still works correctly.
Q: What is a "bad block" in a hard drive?
Physical damage?
Click to expand...

Usually, yes. It is not really possible to manufacture a truly "perfect"
hard disk even today. Onboard controllers have become smarter and with
automatic defect relocation schemes drives appear to be defect free deal, at
least in the onset. Over time, as the media inside wears down additional bad
spots can develop.

Advanced disk repair utilities (like the GRC tool, SpinRite, at
http://grc.com/) can sometimes convince the drive's electronics to replace
the bad spot with a good spare.

Sometimes these spots start to spread like wildfire and the drive is soon
rendered unreliable. Other times (much more common) the drive simply
develops a little defect for no readily apparent reason. I have a few like
this that have been running for years and no further defects or bad spots
have appeared.

I've also had at least one 2.1GB Western Digital that was almost totally bad
as per Scandisk yet it still managed to hang on long enough to copy all of
its data with only one lost file! That operation took all night with the
drive making bad "retry" sounds, but when I put in the replacement drive and
placed all the files back on it, the system and its OS were no worse for the
wear. I was amazed...that was the only time I've ever seen that happen.

Basically, keep an eye on your drive. Back up the contents and run a disk
utility every now and then. If the drive seems OK, don't let your guard
totally down...just continue to keep an eye on it and if you see things
start to get worse--get the data off immediately (hard disk drives don't
usually give out as many warnings as the WD unit above...) and get a new
drive.
Note: please don't give me TinyURL addresses.
Click to expand...

I don't use that service, and have never tried it, but why not?

William
 
William R. Walsh whispers:
Hi!


Usually, yes. It is not really possible to manufacture a truly "perfect"
hard disk even today. Onboard controllers have become smarter and with
automatic defect relocation schemes drives appear to be defect free deal, at
least in the onset. Over time, as the media inside wears down additional bad
spots can develop.
Click to expand...
[... explanations about bad blocks ...]

Thank you for the info.
This helps me.
I don't use that service, and have never tried it, but why not?
Click to expand...

I am getting lots of spam/porn "hidden" as TinyURL links (e.g.
http://www.mycrappypornsite.com -> http://tinyurl.com/foobar )

[]s
 
Chaos said:
I have an oldish 800MB hard drive here which is still working (it
stores some audio files).

Recently, after a power surge, it developed a "bad block" (4kb
marked as bad), but it still works correctly.

Q: What is a "bad block" in a hard drive?
Physical damage?
Click to expand...

Not necessarily. Data is stored in sectors, each of which is
preceded by an identification block. The data in both the sector
proper and the identification block are normally protected by
CRCs, to detect any errors. Your power surge could have induced
something in the heads while passing over those areas and
corrupted them. If in the data section the error will go away
after writing new data there. If in the identification block the
sector is lost, because modern drives have no user available
method of low level formatting.

However all drives fail. The only question is when. So, keep
backups if you value your data.
 
William R. Walsh said:
Hi!


Usually, yes. It is not really possible to manufacture a truly "perfect"
hard disk even today. Onboard controllers have become smarter and with
automatic defect relocation schemes drives appear to be defect free deal, at
least in the onset. Over time, as the media inside wears down additional bad
spots can develop.

Advanced disk repair utilities (like the GRC tool, SpinRite, at
http://grc.com/) can sometimes convince the drive's electronics to replace
the bad spot with a good spare.

Sometimes these spots start to spread like wildfire and the drive is soon
rendered unreliable. Other times (much more common) the drive simply
develops a little defect for no readily apparent reason. I have a few like
this that have been running for years and no further defects or bad spots
have appeared.

I've also had at least one 2.1GB Western Digital that was almost totally bad
as per Scandisk yet it still managed to hang on long enough to copy all of
its data with only one lost file! That operation took all night with the
drive making bad "retry" sounds, but when I put in the replacement drive and
placed all the files back on it, the system and its OS were no worse for the
wear. I was amazed...that was the only time I've ever seen that happen.
Click to expand...

I have similiar experience.
I had an 40GB IBM drive. There were sometimes random problems - some files
couldnt be read, drive couldnt boot, clicking sounds were heard. After
reformatting the HDD there were no bad sectors, but in a week, problems were
back again... the drive was really unreliable.
So I sent it back to store and they gave me new (Maxtor) and its OK now...

Zdenek Sojka
 
CBFalconer([email protected]) whispers:
Not necessarily. Data is stored in sectors, each of which is
preceded by an identification block. The data in both the sector
proper and the identification block are normally protected by
CRCs, to detect any errors. Your power surge could have induced
something in the heads while passing over those areas and
corrupted them. If in the data section the error will go away
after writing new data there. If in the identification block the
sector is lost, because modern drives have no user available
method of low level formatting.
Click to expand...

OK, Thanks.
However all drives fail. The only question is when. So, keep
backups if you value your data.
Click to expand...

I have backup, but since it's mainly rare MP3 files, the problem would be
downloading them again.

Thanks for all that helped!
--
Chaos Master®, posting from Brazil. REPLY TO GROUP!
"People told me I can't dress like a fairy.
I say, I'm in a rock band and I can do what the hell I want!"
-- Amy Lee


Outgoing messages are certified virus-free.
They're plain text, anyway.
 
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