bad sectors on a mybook WD usb drive


R

Rod Speed

sobriquet said:
I've lost some data on a 2 tb WD mybook usb drive. When
I did a full scan, it found something like 3 mb in bad sectors.
However, when I reformatted the drive, somehow all bad sectors were
recovered. Apparently, there is some redundancy in diskspace, so it
can allocate some of that extra space to substitute for the bad
sectors on disk when it's just a small section of bad sectors.

Yes, all modern hard drives have spare sectors
that can be used as substitutes for bad sectors.
The disk is also able to pass the short drive test (in winDLG
under xp), that it used to fail, before I reformatted the drive.
Now I wonder if the fact that previously bad sectors have occurred and
I've lost data, is that increasing the likelyhood that this might happen again?

Yes, that many bad sectors does indicate a problem with
the drive or that the drive is running much too hot etc.
Is the drive less reliable in any way once a small
number of bad sectors have been identified

Yes, and 3MB is not a small number of bad sectors.
(even though the bad sectors are no longer visible after the drive has been
formatted again and other drivespace is substituted for the bad sectors)?

Yes, it either indicates that the drive is dying, or that its running stinking hot etc.
Below is the original log from chdsk when the bad sectors were found:

chkdsk isnt a very useful indication of the health of the drive.

You really need a proper SMART report on the drive.

That isnt necessarily that easy to get for free with an external drive.
 
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S

sobriquet

Yes, all modern hard drives have spare sectors
that can be used as substitutes for bad sectors.


Yes, that many bad sectors does indicate a problem with
the drive or that the drive is running much too hot etc.


Yes, and 3MB is not a small number of bad sectors.


Yes, it either indicates that the drive is dying, or that its running stinking hot etc.


chkdsk isnt a very useful indication of the health of the drive.

You really need a proper SMART report on the drive.

That isnt necessarily that easy to get for free with an external drive.


Well, with winDLG, it does say the SMART status is OK for the device,
and I can get more detailed SMART info.

Here is a screenshot of the SMART info:
http://img11.imageshack.us/img11/74/wdmybook.jpg
 
R

Rod Speed

sobriquet wrote
Well, with winDLG, it does say the SMART status is OK for the device,

That never means much, its the detailled values that matter.
and I can get more detailed SMART info.

It isnt at all clear what that actually means, particularly what the warranty field means.

And the reallocated sector entry and the temperature entry make no sense either.

The Everest SMART report is much more readable,
but doesnt work with external drives in the free version.

smartclt from a linux bootable cd might, and HDSentinal might, but it isnt free.
 
S

sobriquet

sobriquet wrote






That never means much, its the detailled values that matter.


It isnt at all clear what that actually means, particularly what the warranty field means.

And the reallocated sector entry and the temperature entry make no sense either.

The Everest SMART report is much more readable,
but doesnt work with external drives in the free version.

smartclt from a linux bootable cd might, and HDSentinal might, but it isnt free.

The version I've tried from HDSentinel wasn't up to date, but perhaps
the version (5.30) of Everest on demonoid will provide more detailed
SMART info on the drive. I'm busy with the drive now, but I'll soon
follow up on this with a screenshot of the Everest SMART info of the
drive.
 
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S

sobriquet

I assume that is 3 MB (which is 8'000'000'000 times more,
"mb" is milli-bit, you want Mega-Byte). That is a lot.

Millibit would make sense in this discussion (since computers don't
deal with fractional bits), so obviously mb means megabyte, like tb
means terrabyte. I'm sloppy with capitals sometimes, sorry.

I thought 3 MB was not really that much in proportion to the total
size of the drive (2 TB = 2 * 1024 * 1024 MB = 2097152 MB)
That is also normal. This "recovery" is only useful
if the defects are not the fault of the drive.


Not necessarily. It depends on the reason. If it is the drives
own fault, about 10 or more bad sectors are pretty bad.
If it is extern influence (vibration, bad PSU,...) even
a very, very large number like yours does not necessary
say the drive is unreliable after (!) the external problem
has been corrected.

How much redundant space does a typical 2 TB drive have to replace bad
sectors?
The drive was in operation on an uneven surface and perhaps it moved
around or bumped slightly
during operation.
I hope solid state disks will become more affordable soon, as they
seem more resilient to minor shocks.
The "smart status" is over-optimistic in most cases.


It is hard to say anything from this, as the raw values
are missing. It looks as the defects were actually not
replaced but really recoverd (attribute 5 is still
at value 200) and nothing else is suspicuous.
This looks like the sectors are fine, but something
interferred with the write operation.

I have another screenshot that also shows the raw values.

http://img713.imageshack.us/img713/5343/everestje.jpg
How have you handled the drive? Moved it around
or bumped it during operation? Used it with not too
clean power? Used it on a surface that vibrated or
was otherwise mechanically unstable?

Well, in a typical situation, I might have the drive on the desk and
then being somewhat absent minded, I might be drumming along with some
music with my hands on the desk a bit too enthusiastically, which
might make the disk vibrate too much.
I dunno how sensitive these drives are and how much of a shock might
pose a serious problem during reading from or writing to the drive.
 
A

Arno

Millibit would make sense in this discussion (since computers don't
deal with fractional bits), so obviously mb means megabyte, like tb
means terrabyte. I'm sloppy with capitals sometimes, sorry.

The "m" is not that bad, but "b" is bit while "B" is Byte.
I thought 3 MB was not really that much in proportion to the total
size of the drive (2 TB = 2 * 1024 * 1024 MB = 2097152 MB)

Defect sectors should be counted in number per device.

3MB is about 6000 defective secotrs, which is a massive
number. Typically drives are highly suspicuous from 10
defectives onwards and I have only seen one drive so far
with more than 50 defects that was not dying (it got
200 defects in a day and then never any additional ones,
I suspect vibration from some work being done next to the
computer).

[...]
How much redundant space does a typical 2 TB drive have to replace bad
sectors?
The drive was in operation on an uneven surface and perhaps it moved
around or bumped slightly
during operation.
I hope solid state disks will become more affordable soon, as they
seem more resilient to minor shocks.

The problem is less the reallocation space, and more that for each
defective sector there is a very real chance the data stored in it
is gone.

If you do a verify read that risk is mostly eleminated if the
reason is not a defective drive, but an environmental problem.

[...]
I have another screenshot that also shows the raw values.

Except for the temperature, the drive looks perfectly
healty. The temperature is 63C (if the encoding is
the same as on other WD drives) and 63C is deep
into HDD killer territory. More than 50C is reason
for real concern and typically above the maximum
allowed temperature. From 65-75C or so, the mechanics
and electronics starts to fail (non-permanently, but
ageing very fast, like beging dead from old age within
weeks-months), so that is possibly were your
defects came from: You got the disk so hot it
stopped working right.

You need to bring donwn the temperature.

The non-perfect scores on the "Worst" vlaue for
C5 and C8 indicate, there was a serious problem
but it is gone at the moment.
Well, in a typical situation, I might have the drive on the desk and
then being somewhat absent minded, I might be drumming along with some
music with my hands on the desk a bit too enthusiastically, which
might make the disk vibrate too much.
I dunno how sensitive these drives are and how much of a shock might
pose a serious problem during reading from or writing to the drive.

Maybe. Lound sounds can cause problems. Here is an
enlightening video demonstrating the effect:


This can also cause write defects, were the data is
unreadable (i.e. you have data loss) but the sector is again
fine after an overwrite.

Arno
 
A

Arno

IIUC, WD's temperature attribute assigns a normalised value of 100 to
a temperature of 50C. A value of 89 would then suggest that the
temperature is 61C.
I could be wrong, though ...

With the WDs I have the raw attribute seems to be C directly.

Arno
 
B

Bob

Arno said:
Except for the temperature, the drive looks perfectly
healty. The temperature is 63C (if the encoding is
the same as on other WD drives) and 63C is deep
into HDD killer territory. More than 50C is reason
for real concern and typically above the maximum
allowed temperature. From 65-75C or so, the mechanics
and electronics starts to fail (non-permanently, but
ageing very fast, like beging dead from old age within
weeks-months), so that is possibly were your
defects came from: You got the disk so hot it
stopped working right.

You need to bring donwn the temperature.

Amen. The WD20EARS has a 60C spec for maximum operating temperature.
It's hard to imagine what WD did to get that very low power drive
(6.0 Watts read/write, 3.7 Watts idle) to heat up that much in that
external enclosure.
Maybe. Lound sounds can cause problems. Here is an
enlightening video demonstrating the effect:


This can also cause write defects, were the data is
unreadable (i.e. you have data loss) but the sector is again
fine after an overwrite.

My lesson in vibration effects came when I had a very bad tape drive that
I was using one final time to recover data from some old DC600-style tapes.
A bad roller was causing a lot of vibration, and to stop a spew of disk
errors I had to pull the tape drive out of the housing it shared with the
disk drives. (Recovered the data -- junked the tape drive and tapes.)
 
R

Rod Speed

sobriquet wrote
It isnt in fact all that many now that we can see the SMART data.

Turns out to only be 3 bad sectors.
Screenshot of Everest SMART info of the same drive:

Thats much better. That shows 3 reallocated sectors which
isnt too bad given the utterly obscene temperature of 63C.

The temperature is certainly the problem and the
drive will be fine if you can stop it getting that hot.

Not easy to stop it getting that hot tho, particularly in the
summer without air conditioning etc with those external drives.
 
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R

Rod Speed

Rod Speed wrote
sobriquet wrote
It isnt in fact all that many now that we can see the SMART data.
Turns out to only be 3 bad sectors.

And 3 more pending.
Thats much better. That shows 3 reallocated sectors which
isnt too bad given the utterly obscene temperature of 63C.

And its actually been to 87, thats completely and utterly obscene.
The temperature is certainly the problem and the
drive will be fine if you can stop it getting that hot.
Not easy to stop it getting that hot tho, particularly in the
summer without air conditioning etc with those external drives.

I'd be returning it if it was mine, but that wouldnt be a warranty claim and how
easy it would be to do that depends on your country and its consumer laws.

The technical term is unfit for purpose in countrys with a legal system derived from the british system.

I cant remember the detail with Dutch law.
 
A

Arno

Amen. The WD20EARS has a 60C spec for maximum operating temperature.
It's hard to imagine what WD did to get that very low power drive
(6.0 Watts read/write, 3.7 Watts idle) to heat up that much in that
external enclosure.

Indeed. It is possible that the WD20EARS uses a different
raw temperature format than other WD drives. I have a
WD10EAVS, a WD15EADS and two WD notebook drives, a
WD5000BEVT and a WD3200BEVT, all have the temperature
in C in the raw temperature value. Also the "worst"
attribute in the screenshot of the OP indicates that the
disk was hotter. Add to that the 2% or so accuracy error of
the sensor and the disk may have reached > 67C or so.

Also note that while the disk may be operated up to
60C, it will still age much faster. The typical 5 years
component lifetime is usually specified at 25C and
halves every 10C or so. At 65C the drive has a component
life of 4 months, after which its MTBF becomes unspecified.
This does not mean the drive will necessarily die. It
typically becomes a lot more likely though.
My lesson in vibration effects came when I had a very bad tape drive
that I was using one final time to recover data from some old
DC600-style tapes. A bad roller was causing a lot of vibration, and
to stop a spew of disk errors I had to pull the tape drive out of
the housing it shared with the disk drives. (Recovered the data --
junked the tape drive and tapes.)

Interesting!

Arno
 
R

Rod Speed

sobriquet wrote
Millibit would make sense in this discussion (since computers don't
deal with fractional bits), so obviously mb means megabyte, like tb
means terrabyte. I'm sloppy with capitals sometimes, sorry.
I thought 3 MB was not really that much in proportion to the total
size of the drive (2 TB = 2 * 1024 * 1024 MB = 2097152 MB)

What matters is the number of sectors affected.

Turns out its only 6 and thats not too bad given the
utterly obscene temperature the drive peaked at, 87C.
How much redundant space does a typical 2 TB drive have to replace bad sectors?

Varys with the drive, but a hell of a lot more than the 6 you have a problem with.

But what matters is that if you have more than a few due to the drive
itself and not something external to the drive like vibration etc, then
its evidence that the drive is dying long before you use up all the spares.

You can get occassional bads due to mains failures with some drives that
dont handle loss off power that well, but that really the only situation where
a small number of bad sectors is acceptible. With everything else, its always
an indication that the drive is dying if the problem isnt external to the drive.

In your case the drive got absolutely stinking hot at 87C max and
thats what produced the bad sectors. If you can stop it getting
anything like that hot again, the drive should be fine life wise.

Not that easy to do tho with an external drive with poor cooling of the drive.
The drive was in operation on an uneven surface and
perhaps it moved around or bumped slightly during operation.

Nar, its definitely the grossly excessive temperature that was the problem.

Interesting that the stupid WDdlg didnt even mention any problem.

Utterly obscene, actually.
I hope solid state disks will become more affordable
soon, as they seem more resilient to minor shocks.

Yes, but your problem was not minor shocks.
I have another screenshot that also shows the raw values.
Well, in a typical situation, I might have the drive on the desk and
then being somewhat absent minded, I might be drumming along
with some music with my hands on the desk a bit too enthusiastically,
which might make the disk vibrate too much.
I dunno how sensitive these drives are and how much of a shock might
pose a serious problem during reading from or writing to the drive.

It should handle that fine, but not say the drive falling over etc.
 
R

Rod Speed

Bob said:
Amen. The WD20EARS has a 60C spec for maximum operating temperature.
It's hard to imagine what WD did to get that very low power drive
(6.0 Watts read/write, 3.7 Watts idle) to heat up that much in that
external enclosure.

In fact the Everest SMART report shows that it actually got to 87C and that is utterly obscene.
 
S

sobriquet

Rod Speed wrote






And 3 more pending.






And its actually been to 87, thats completely and utterly obscene.


I'd be returning it if it was mine, but that wouldnt be a warranty claim and how
easy it would be to do that depends on your country and its consumer laws.

The technical term is unfit for purpose in countrys with a legal system derived from the british system.

I cant remember the detail with Dutch law.

http://img62.imageshack.us/img62/5758/everest1q.jpg

So that means one of my internal hitachi drives reached a temperature
of 150C?!
 
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R

Robert Nichols

:In fact the Everest SMART report shows that it actually got to 87C and that is utterly obscene.

I don't get that from the report.

Attribute Description Threshold Value Worst Data
--------------------- --------- ----- ----- -------------
C2 Temperature 0 89 87 63

That "87" is the _normalized_ parameter -- a value that drops with
increasing temperature and indicates "fail" status when it falls to the
threshold value of 0. Note that the current value is "89" while the
value in the "Worst" column is "87". That makes no sense if those
values are actual temperatures. No, it appears that the drive was
never much hotter than at the time that measurement was taken.

It would be really interesting to see what those numbers are when the
drive is first switched on after an extended power off cooldown, when
the drive is still near the ambient temperature.
 
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S

sobriquet

Nope, 40C

But that 40 number for the hitachi drive is in the same column as the
63 for the WD drive.. and I don't understand the relationship between
the raw values and the value/worst numbers, or does that differ
between various brands/models of HDs?
 

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