OT: bad sector remapping

[D Yuniskis]

Hi,

I'm putting together a laptop for a friend. Clean install
of XP. Add required drivers, etc.

At this point, I would normally take a snapshot of the
disk (restoring from snapshot is *much* quicker than
reinstalling, etc.).

Doing so, Clonezilla claims a couple of bad sectors
(I'd have to doublecheck the log to see which tool
complained).

I believe this as the "disk check" built into the
BIOS gave a supper informative "Error #2" or somesuch.
Machine operates normally, otherwise.

So, is XP smart enough to avoid the bad sector?
Or, has it just not stumbled across it, yet?

I had thought modern PATA drives had finally adopted
the "grown defect table" support SCSI drives have
had. And, that the drive itself would take care
of the necessary housekeeping (i.e., to map a "good"
physical sector in to replace the bad one).

I've checked the Fujitsu site (seems they have sold
off their drive business to Toshiba?) but nothing like
a "low level format" utility there -- or any other
diagnostic/maintenance tool.

It's a 100G drive so I'd hate to discard it. But, I
think I have some 160's I could call on to replace it
if push comes to shove...

<frown> I hate this time of year! :-/

Thx,
--don

 

[Przemek Klosowski]

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis wrote:

Doing so, Clonezilla claims a couple of bad sectors (I'd have to
doublecheck the log to see which tool complained).
...
So, is XP smart enough to avoid the bad sector? Or, has it just not
stumbled across it, yet?

No, it's in the disk firmware. If it can recover data using its array of
tricks (error correction, re-seeks and recalibration), it'll remap the
bad sectors, and return correct data, possibly after a significant delay.
If it can't recover the data, it reports disk reading errors, and XP
can't do anything about it.

I had thought modern PATA drives had finally adopted the "grown defect
table" support SCSI drives have had. And, that the drive itself would
take care of the necessary housekeeping (i.e., to map a "good" physical
sector in to replace the bad one).

Since late 1990s practically all disks have the firmware diagnostics
called SMART. They can be read from ATA, SATA, SAS and even USB
interfaces. In Linux SMART data can be read via the skdump and smartctl
commands, and a very nice disk utility called 'palimpsest' that can read
SMART data, run SMART tests, and even characterize disk speed dependence
on sector location. Some BIOSes display SMART status, but w/o much detail.
There are manufacturer utilities to show SMART; they should be vendor-
independent, actually, because SMART is almost standard.

While the firmware can swap out recoverable bad sectors, there was a
Google paper showing that any bad sectors are a significant predictor of
a future complete disk failure. Watch for Reallocated Sector Count
(recovered errors) and especially Current Pending Sector (unrecoverable
errors).

frown> I hate this time of year! :-/

Bah, humbug, as well

 

[D Yuniskis]

Hi Przemek,

On 12/20/2010 9:04 PM, Przemek Klosowski wrote:

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis wrote:

Doing so, Clonezilla claims a couple of bad sectors (I'd have to
doublecheck the log to see which tool complained).
...
So, is XP smart enough to avoid the bad sector? Or, has it just not
stumbled across it, yet?

No, it's in the disk firmware. If it can recover data using its array of
tricks (error correction, re-seeks and recalibration), it'll remap the
bad sectors, and return correct data, possibly after a significant delay.
If it can't recover the data, it reports disk reading errors, and XP
can't do anything about it.

Yes, that's what I expected. So, the fact that XP didn't complain
during the format, install and a subsequent "defragment" suggests it
simply didn't *touch* that sector (?).

By contrast, Clonezilla *did* (suggesting that Windows had put
something *in* it) access it and complain.

<frown>

I stumbled across "MHDD" which *seems* like it should be able
to do what I need. Of course, at an hour per pass, it will
be a while before I can go through the entire install with
Clonezilla chaser.

I'll post back when I have more conclusive results.

I had thought modern PATA drives had finally adopted the "grown defect
table" support SCSI drives have had. And, that the drive itself would
take care of the necessary housekeeping (i.e., to map a "good" physical
sector in to replace the bad one).

Since late 1990s practically all disks have the firmware diagnostics
called SMART. They can be read from ATA, SATA, SAS and even USB
interfaces. In Linux SMART data can be read via the skdump and smartctl
commands, and a very nice disk utility called 'palimpsest' that can read
SMART data, run SMART tests, and even characterize disk speed dependence
on sector location. Some BIOSes display SMART status, but w/o much detail.
There are manufacturer utilities to show SMART; they should be vendor-
independent, actually, because SMART is almost standard.

While the firmware can swap out recoverable bad sectors, there was a
Google paper showing that any bad sectors are a significant predictor of
a future complete disk failure. Watch for Reallocated Sector Count
(recovered errors) and especially Current Pending Sector (unrecoverable
errors).

I thought the paper mentioned how *bad* SMART was at predicting
failures (?)

frown> I hate this time of year! :-/

Bah, humbug, as well

<grin> End of year replacing equipment (and finding new homes
for the old stuff) always ends up eating up far more time than
I expect! :-/

 

[David Brown]

On 21/12/2010 07:30, D Yuniskis wrote:

Hi Przemek,

On 12/20/2010 9:04 PM, Przemek Klosowski wrote:
On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis wrote:

Doing so, Clonezilla claims a couple of bad sectors (I'd have to
doublecheck the log to see which tool complained).
...
So, is XP smart enough to avoid the bad sector? Or, has it just not
stumbled across it, yet?

No, it's in the disk firmware. If it can recover data using its array of
tricks (error correction, re-seeks and recalibration), it'll remap the
bad sectors, and return correct data, possibly after a significant delay.
If it can't recover the data, it reports disk reading errors, and XP
can't do anything about it.

Yes, that's what I expected. So, the fact that XP didn't complain
during the format, install and a subsequent "defragment" suggests it
simply didn't *touch* that sector (?).

By contrast, Clonezilla *did* (suggesting that Windows had put
something *in* it) access it and complain.

The disk will only report bad sectors when /reading/. If it notices a
failure during a write (this is very rare), it will silently re-locate
that sector to one of its spare sectors (unless, of course, the drive is
so bad that it runs out of spares). When reading a sector, the disk can
correct a number of errors. If the errors reach a certain threshold,
then again the disk will silently re-locate the sector and return the
corrected data. But if there were uncorrectable errors, the disk
returns an error message.

Think about what happens during an NTFS format. Assuming it is a
"quick" format, very little is actually written to the disk - just the
superblocks and a skeleton MFT. And /nothing/ is read - thus bad
sectors will not be found. During installation of XP, very little is
read - most access is writing to the disk, so again the chances of
spotting a failure are small. In use, XP will obviously read from the
disk - but only the sectors it needs, which is a small proportion of the
total written data. But when Clonezilla is copying a disk, it will read
/everything/ - if there are errors, these will show up.

It is also possible that Clonezilla does a more low-level read and gets
information about poor or failing sectors rather than just unrecoverably
failed sectors. I don't know if that's the case or not - you would have
to check in the Clonezilla documentation.

 

[Robert Roland]

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis
<not.going.to.be@seen.com> wrote:

So, is XP smart enough to avoid the bad sector?

Yes, but not "on the fly", as the drive does internally. If you run a
chkdsk /F/R, Windows will test all sectors and try to relocate the
data in the bad sectors to a good sector. It is unlikely the recovery
will succeed, but at least it will let you know which file is lost.

Or, has it just not stumbled across it, yet?

Quite possible. There are lots of files that are almost never used,
and even quite a few that are never used in normal operation.

I had thought modern PATA drives had finally adopted
the "grown defect table" support SCSI drives have
had.

They do. The problem is that this defect table is of limited size, and
when it is full, the drive has to start marking additional bad sectors
the old fashioned way.

This means that once you see the first bad sector, there are actually
hundreds, maybe thousands of bad sectors already. This is caused by a
fault in the drive, and this fault will cause more bad sector to
appear with time.

I've checked the Fujitsu site (seems they have sold
off their drive business to Toshiba?) but nothing like
a "low level format" utility there

Modern drives use a voice coil to position the heads. Such drives
cannot be low level formatted, because they need the servo information
on the platters to position the heads. If you erase the platters with
a strong magnetic field, the drive will start to hopelessly clank the
heads against the end stop, desperately trying to find the servo
information.

-- or any other
diagnostic/maintenance tool.

That's poor customer service. But if the BIOS says the drive is bad,
and a different drive tests OK, then it *is* bad.

It's a 100G drive so I'd hate to discard it.

The drive is broken. If you don't want to discard it, use it as a
paperweight.

If you continue to use the drive, you will experience neverending,
random problems, and you may hate Windows for being so unstable. Note
that a bad sector propping up in the page file will cause a bluescreen
crash with a message suggesting a memory error. Once sector zero dies,
you will no longer be able to use the drive on a Wintel BIOS based
machine.

Do yourself a favor: Replace the drive.
--
RoRo

 

[d_s_klein]

On Dec 21, 6:28 am, Robert Roland <f...@ddress.no> wrote:

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis

not.going.to...@seen.com> wrote:
So, is XP smart enough to avoid the bad sector?

Yes, but not "on the fly", as the drive does internally. If you run a
chkdsk /F/R, Windows will test all sectors and try to relocate the
data in the bad sectors to a good sector. It is unlikely the recovery
will succeed, but at least it will let you know which file is lost.

Not *exactly* correct. If chkdsk encounters an unused bad sector it
will it to the bad sector list. A status line from chkdsk reports the
number of bad sectors if it is non-zero. That sector will be avoided
(not remapped) until the next re-format.

Do yourself a favor: Replace the drive.
--

I agree 1000%. The cost of the drive (1T < $100) is dwarfed by the
cost of the data.

RoRo

RK

 

[Meat Plow]

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis wrote:

Hi,

I'm putting together a laptop for a friend. Clean install of XP. Add
required drivers, etc.

At this point, I would normally take a snapshot of the disk (restoring
from snapshot is *much* quicker than reinstalling, etc.).

Doing so, Clonezilla claims a couple of bad sectors (I'd have to
doublecheck the log to see which tool complained).

I believe this as the "disk check" built into the BIOS gave a supper
informative "Error #2" or somesuch. Machine operates normally,
otherwise.

So, is XP smart enough to avoid the bad sector? Or, has it just not
stumbled across it, yet?

No NTFS is not smart enough to mark bad clusters. Novel HPFS was and I've
seen it in action. If the NTFS journal of MFT does not ride on the bad
sector/cluster then the operating system would know nothing about it
unless you ran a chkdsk. Most decent disc cloners will not clone a file
system with bad blocks/sectors/clusters. Acronis Easy Migrate which I use
won't.


comp.arch.embedded removed.



--
Live Fast, Die Young and Leave a Pretty Corpse

 

[Dave Platt]

In article <iep90h$a0t$2@news.eternal-september.org>,
Przemek Klosowski <przemek@tux.dot.org> wrote:

While the firmware can swap out recoverable bad sectors, there was a
Google paper showing that any bad sectors are a significant predictor of
a future complete disk failure. Watch for Reallocated Sector Count
(recovered errors) and especially Current Pending Sector (unrecoverable
errors).

That matches what I've seen, over the past ten years of doing
hard-drive support at TiVo for DVR applications.

It's common for drives to have a small number of "grown" defects over
its lifetime (i.e. bad sectors which were not detected during factory
formatting, but have "gone bad" during use). However, once you see
more than a very few of these, or get several of them occurring in a
fairly short period of time, it's a pretty good sign that the drive is
on a rapidly-descending path to total failure, and it's time to back
up it (if you haven't already, shame on you) and replace it.

I discussed the issue with engineers from a couple of hard-drive
manufacturers, and believe that there's a good reason why this is the
case. In modern hard drives, the read/write head is flying over the
media surface at a *very* low height -- the width of a human hair is
huge by comparison, and even a particle of cigarette smoke looks like
a boulder. If there's any contaminating particle at all on the disk
surface, it'll get between the head and the surface and cause the head
to "bounce" or scrape. Even if it doesn't force the head away from
the platter, it causes enough friction to heat up the tiny read/write
head and change its electrical characteristics, resulting in a bad
read (the engineers used the term "thermal asperity" to refer to this
sort of event).

A major reason for the development of bad sectors, is physical damage:
"head slap", in which the head actually hits the platter and knocks
some particles loose. Thie can happen if the drive or computer is
banged or moved sharply while the drive is spinning, or even when it's
powered off. If these particles remain on the disk surface (or fly
away and then land again, elsewhere) they're likely to be hit by the
head during a subsequent revolution... which can cause more scraping
or even slapping of the head, more damage to the surface, and the
creation of more loose particles. Although the drives have a fiber
filter in the air-flow path which is intended to catch these
particles, it's never 100% effective... and so the amount of
contamination builds up as time goes by, and the problem snowballs and
the drive goes downhill towards failure.

After playing around with a number of error-management ideas at TiVo,
I came to the conclusion that it wasn't worth bothering with. A drive
which shows a significant number of reallocated (or pending-
reallocation) sectors, probably doesn't have very long to live...
its performance will degrade (due to the need to retry reads on
sectors that are going bad) and it will lose more and more data
(unrecoverable errors). The best filesystem- and application-level
error management techniques I could dream up, wouldn't have extended
the life of a failing drive enough to be worth the effort and
complexity.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Dave Platt]

In article <ldb1h61emh2c0qlfrhjf3ogeulfebc0hl2@4ax.com>,
Robert Roland <fake@ddress.no> wrote:

Do yourself a favor: Replace the drive.

Excellent advice. The cost of a simple replacement is relatively
small (around $50), the cost to you of lost productivity and/or data
could be far higher if your current drive fails completely, and your
current drive probably *will* fail completely before long no matter
what you do.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[D Yuniskis]

Hi Robert,

On 12/21/2010 7:28 AM, Robert Roland wrote:

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis
not.going.to.be@seen.com> wrote:

So, is XP smart enough to avoid the bad sector?

Yes, but not "on the fly", as the drive does internally. If you run a
chkdsk /F/R, Windows will test all sectors and try to relocate the
data in the bad sectors to a good sector. It is unlikely the recovery
will succeed, but at least it will let you know which file is lost.

My point is that windows' (possessive) handling of the error
must be done at a higher level (abstraction) than the remapping
that the drive is *supposed* to be doing. I.e., it modifies
some structure in the filesystem that *it* (windows) maintains;
and does NOT force the drive to remap the sector.

[this makes sense if the "application" sits in userland and
isn't tightly integrated into the OS -- otherwise, the OS
would have to export the "remap bad HARDWARE sector" facility
in its API]

E.g., I re-did the install. Chkdsk. Defrag. etc. and partclone
(part of Clonezilla) *still* complained about a bad sector.

So, what I did last night (while waiting for the moon to creep
into shadow) was to run this utility. repeatedly. (takes a bit
over an hour to scan the drive). Each time, the same sector was
flagged as "bad". Sector number corresponded with the one
reported by partclone.

Then, had that utility "remap" the sector. And, another scan.

Sector no longer reported as bad. Though in its place, the
"new" sector shows an increased access time (utility graphically
depicts access times of each sector -- so, you can "see" each
time the head moves to a new cylinder as the first access in
that cylinder will be higher than all subsequent ones) no doubt
a result of the drive having to "fetch" the remapped cyclinder.

Ran the BIOS "test hard disk" utility. Passed without complaint.

Reinstalled windows. chkdsk. defragment. Still no complaints.

Ran clonezilla. Successfully completed in ~4 minutes (i.e., I
can now do a "restore" in about the same amount of time -- not
the hours that a new windows install would require!)

Or, has it just not stumbled across it, yet?

Quite possible. There are lots of files that are almost never used,
and even quite a few that are never used in normal operation.

But, in theory, chkdsk would have examined EVERY sector on
the drive, even those not currently in use by "files" (or
"superblock")

I had thought modern PATA drives had finally adopted
the "grown defect table" support SCSI drives have
had.

They do. The problem is that this defect table is of limited size, and
when it is full, the drive has to start marking additional bad sectors
the old fashioned way.

This means that once you see the first bad sector, there are actually
hundreds, maybe thousands of bad sectors already. This is caused by a
fault in the drive, and this fault will cause more bad sector to
appear with time.

I've checked the Fujitsu site (seems they have sold
off their drive business to Toshiba?) but nothing like
a "low level format" utility there

Modern drives use a voice coil to position the heads. Such drives
cannot be low level formatted, because they need the servo information
on the platters to position the heads. If you erase the platters with
a strong magnetic field, the drive will start to hopelessly clank the
heads against the end stop, desperately trying to find the servo
information.

Yes, we bulk erase (and/or drill a 3/8" dia hole through the
drive) drives headed out for "scrap". Amusing to see folks
try to resurrect a drive that has been bulk erased (but not
yet drilled).

-- or any other
diagnostic/maintenance tool.

That's poor customer service. But if the BIOS says the drive is bad,
and a different drive tests OK, then it *is* bad.

BIOS only complained when explicitly asked to "test hard drive".
Obviously did a surface scan and complained when it encountered this
sector (this is speculation on my part; error message was totally
useless -- the equivalent of "check engine").

It's a 100G drive so I'd hate to discard it.

The drive is broken. If you don't want to discard it, use it as a
paperweight.

If you continue to use the drive, you will experience neverending,
random problems, and you may hate Windows for being so unstable. Note
that a bad sector propping up in the page file will cause a bluescreen
crash with a message suggesting a memory error. Once sector zero dies,
you will no longer be able to use the drive on a Wintel BIOS based
machine.

Do yourself a favor: Replace the drive.

As I said, I have several other drives. But, my experience has
been that getting *at* the drive often results in damage to the
case (the 'snaps" on these cheap plastic clamshells invariably
break). So, if it boils down to open the case to replace the drive,
I'll turn the disk off in the BIOS and use it as a diskless
workstation (which pretty much eliminates it's usefulness as
a laptop -- just turns it into a "portable, *wired* computer")

Or, "recycle" it.

For now, everything *looks* like it is working. So, I'll
install the rest of the applications and periodically
"scan" the disk by doing periodic partclones. (I can ALWAYS
discard it at a later date! :> )

Thanks!

 

[D Yuniskis]

On 12/21/2010 9:04 AM, d_s_klein wrote:

On Dec 21, 6:28 am, Robert Roland<f...@ddress.no> wrote:
On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis

not.going.to...@seen.com> wrote:
So, is XP smart enough to avoid the bad sector?

Yes, but not "on the fly", as the drive does internally. If you run a
chkdsk /F/R, Windows will test all sectors and try to relocate the
data in the bad sectors to a good sector. It is unlikely the recovery
will succeed, but at least it will let you know which file is lost.

Not *exactly* correct. If chkdsk encounters an unused bad sector it
will it to the bad sector list. A status line from chkdsk reports the

But, is this list at filesystem level or *within* the drive (e.g.,
"grown defect list")?

number of bad sectors if it is non-zero. That sector will be avoided
(not remapped) until the next re-format.

This suggests the list is in an OS-maintained structure and NOT in
the drive itself. It also suggests that formatting purges the
list (?). I.e., format by itself will just re-introduce the
flakey sector back into the pool of available sectors (until the
next chkdsk)

Do yourself a favor: Replace the drive.

I agree 1000%. The cost of the drive (1T< $100) is dwarfed by the
cost of the data.

Machine will just be used for email and to view camera photos
off SC cards while traveling. As I said elsewhere, opening the
case to replace the drive stands a good chance of damaging the
case (I repair rescued laptops for a local non-profit so I am
well aware of how easily they can be trashed -- having trashed
far too many, myself! :> ). Some laptops are a bit friendlier
for the "common" repairs (swap drives, swap PCI modules, swap
memory -- some are even cooperative in replacing the CD/DVD!).

This one isn't. :-/

The consolation is that if it starts acting up "while traveling",
it can just be dumped into the nearest trash can :>

 

[D Yuniskis]

On 12/21/2010 9:06 AM, Meat Plow wrote:

On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis wrote:

Hi,

I'm putting together a laptop for a friend. Clean install of XP. Add
required drivers, etc.

At this point, I would normally take a snapshot of the disk (restoring
from snapshot is *much* quicker than reinstalling, etc.).

Doing so, Clonezilla claims a couple of bad sectors (I'd have to
doublecheck the log to see which tool complained).

I believe this as the "disk check" built into the BIOS gave a supper
informative "Error #2" or somesuch. Machine operates normally,
otherwise.

So, is XP smart enough to avoid the bad sector? Or, has it just not
stumbled across it, yet?

No NTFS is not smart enough to mark bad clusters. Novel HPFS was and I've
seen it in action. If the NTFS journal of MFT does not ride on the bad
sector/cluster then the operating system would know nothing about it
unless you ran a chkdsk. Most decent disc cloners will not clone a file
system with bad blocks/sectors/clusters. Acronis Easy Migrate which I use
won't.

Actually, in googling for a utility to remap the bad sector,
I stumbled across one that *would* clone a partition with
bad sectors (the bad sectors are probably recorded as "full of
zero, etc."). This would be handy when trying to recover
data from a failing drive as it would let you migrate the
image (defective as it is) to a functional drive where you
could operate on it.

 

[d_s_klein]

On Dec 21, 10:39 am, D Yuniskis <not.going.to...@seen.com> wrote:

On 12/21/2010 9:04 AM, d_s_klein wrote:

On Dec 21, 6:28 am, Robert Roland<f...@ddress.no>  wrote:
On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis

not.going.to...@seen.com>  wrote:
So, is XP smart enough to avoid the bad sector?

Yes, but not "on the fly", as the drive does internally. If you run a
chkdsk /F/R, Windows will test all sectors and try to relocate the
data in the bad sectors to a good sector. It is unlikely the recovery
will succeed, but at least it will let you know which file is lost.

Not *exactly* correct.  If chkdsk encounters an unused bad sector it
will it to the bad sector list.  A status line from chkdsk reports the

But, is this list at filesystem level or *within* the drive (e.g.,
"grown defect list")?

number of bad sectors if it is non-zero.  That sector will be avoided
(not remapped) until the next re-format.

This suggests the list is in an OS-maintained structure and NOT in
the drive itself.  It also suggests that formatting purges the
list (?).  I.e., format by itself will just re-introduce the
flakey sector back into the pool of available sectors (until the
next chkdsk)

There is a bad sector list that is maintained by the OS on the hard
drive as part of the file system. Every file system I have ever
worked with has such a feature, and I date back to the RT-11 days.

Typical method is the mark the sector (cluster) as 'unavailable' -
before- it is attached to a file, and it gets skipped when the OS
searches for the next available sector (cluster).

When you build a new file system, this list typically starts at
"empty". One exception is the Windows floppy format - it scans the
disk and builds a new list every time unless you specifically tell it
not to. There are probably options to the other format routines to
force it to build a new list. (I use chkdsk with surface scan
immediately after formatting.) In the 'pre-IDE' days, one got a chart
with the drive, and format was told about the bad sectors "by hand".

RK

 

[d_s_klein]

On Dec 21, 10:39 am, D Yuniskis <not.going.to...@seen.com> wrote:

Machine will just be used for email and to view camera photos
off SC cards while traveling.  As I said elsewhere, opening the
case to replace the drive stands a good chance of damaging the
case (I repair rescued laptops for a local non-profit so I am
well aware of how easily they can be trashed -- having trashed
far too many, myself!  :> ).  Some laptops are a bit friendlier
for the "common" repairs (swap drives, swap PCI modules, swap
memory -- some are even cooperative in replacing the CD/DVD!).

This one isn't.  :-/

The consolation is that if it starts acting up "while traveling",
it can just be dumped into the nearest trash can  :

Configure it to boot off of a flash drive. Or boot off of a CD, and
use a flash drive for storage. - That way there is no data to recover
after it has breathed its last.

Or realize that you can get a bucket-class laptop for less than you've
'spent' so far on this one.

RK

 

[Dave Platt]

In article <pan.2010.12.21.19.51.19@lmao.lol.lol>,
Meat Plow <mhywatt@yahoo.com> wrote:

Actually, in googling for a utility to remap the bad sector, I stumbled
across one that *would* clone a partition with bad sectors (the bad
sectors are probably recorded as "full of zero, etc."). This would be
handy when trying to recover data from a failing drive as it would let
you migrate the image (defective as it is) to a functional drive where
you could operate on it.

Use at own risk

GNU "ddrescue" can do this - it can make multiple tries to recover
bad sectors, and keeps track of what it's doing so you can restart it
later and try again on the portions of the image it didn't get the
first time.

http://ubuntu-rescue-remix.org/ is a free, bootable "live" CD version
of Linux which has ddrescue included - download, burn, boot, ddrescue
the failing disk to a blank one, then run the normal operating
system's filesystem-level recovery tools on the "clone" disk, and then
check the >bleep< out of any file you manage to salvage.

Then, shred the old drive (or disassemble it and use the platters for
tree decorations).

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Meat Plow]

On Tue, 21 Dec 2010 12:45:53 -0700, D Yuniskis wrote:

On 12/21/2010 9:06 AM, Meat Plow wrote:
On Mon, 20 Dec 2010 18:47:49 -0700, D Yuniskis wrote:

Hi,

I'm putting together a laptop for a friend. Clean install of XP. Add
required drivers, etc.

At this point, I would normally take a snapshot of the disk (restoring
from snapshot is *much* quicker than reinstalling, etc.).

Doing so, Clonezilla claims a couple of bad sectors (I'd have to
doublecheck the log to see which tool complained).

I believe this as the "disk check" built into the BIOS gave a supper
informative "Error #2" or somesuch. Machine operates normally,
otherwise.

So, is XP smart enough to avoid the bad sector? Or, has it just not
stumbled across it, yet?

No NTFS is not smart enough to mark bad clusters. Novel HPFS was and
I've seen it in action. If the NTFS journal of MFT does not ride on the
bad sector/cluster then the operating system would know nothing about
it unless you ran a chkdsk. Most decent disc cloners will not clone a
file system with bad blocks/sectors/clusters. Acronis Easy Migrate
which I use won't.

Actually, in googling for a utility to remap the bad sector, I stumbled
across one that *would* clone a partition with bad sectors (the bad
sectors are probably recorded as "full of zero, etc."). This would be
handy when trying to recover data from a failing drive as it would let
you migrate the image (defective as it is) to a functional drive where
you could operate on it.

Use at own risk



--
Live Fast, Die Young and Leave a Pretty Corpse

 

[Meat Plow]

On Tue, 21 Dec 2010 12:41:57 -0800, Dave Platt wrote:

In article <pan.2010.12.21.19.51.19@lmao.lol.lol>, Meat Plow
mhywatt@yahoo.com> wrote:

Actually, in googling for a utility to remap the bad sector, I
stumbled across one that *would* clone a partition with bad sectors
(the bad sectors are probably recorded as "full of zero, etc."). This
would be handy when trying to recover data from a failing drive as it
would let you migrate the image (defective as it is) to a functional
drive where you could operate on it.

Use at own risk

GNU "ddrescue" can do this - it can make multiple tries to recover bad
sectors, and keeps track of what it's doing so you can restart it later
and try again on the portions of the image it didn't get the first time.

http://ubuntu-rescue-remix.org/ is a free, bootable "live" CD version of
Linux which has ddrescue included - download, burn, boot, ddrescue the
failing disk to a blank one, then run the normal operating system's
filesystem-level recovery tools on the "clone" disk, and then check the
bleep< out of any file you manage to salvage.

Then, shred the old drive (or disassemble it and use the platters for
tree decorations).

I use GParted the fronted for Parted + ntfsprogs in linux to
create,grow,shrink,move,copy,check and label partitions.
Works very well.

This is ported for Windoze:
http://gnuwin32.sourceforge.net/packages/ntfsprogs.htm



--
Live Fast, Die Young and Leave a Pretty Corpse

 

[Didi]

On Dec 21, 7:55 pm, dpl...@radagast.org (Dave Platt) wrote:

In article <iep90h$a0...@news.eternal-september.org>,
Przemek Klosowski  <prze...@tux.dot.org> wrote:

While the firmware can swap out recoverable bad sectors, there was a
Google paper showing that any bad sectors are a significant predictor of
a future complete disk failure. Watch for Reallocated Sector Count
(recovered errors) and especially Current Pending Sector (unrecoverable
errors).

That matches what I've seen, over the past ten years of doing
hard-drive support at TiVo for DVR applications.

It's common for drives to have a small number of "grown" defects over
its lifetime (i.e. bad sectors which were not detected during factory
formatting, but have "gone bad" during use).  However, once you see
more than a very few of these, or get several of them occurring in a
fairly short period of time, it's a pretty good sign that the drive is
on a rapidly-descending path to total failure, and it's time to back
up it (if you haven't already, shame on you) and replace it.

I discussed the issue with engineers from a couple of hard-drive
manufacturers, and believe that there's a good reason why this is the
case.  In modern hard drives, the read/write head is flying over the
media surface at a *very* low height -- the width of a human hair is
huge by comparison, and even a particle of cigarette smoke looks like
a boulder.  If there's any contaminating particle at all on the disk
surface, it'll get between the head and the surface and cause the head
to "bounce" or scrape.  Even if it doesn't force the head away from
the platter, it causes enough friction to heat up the tiny read/write
head and change its electrical characteristics, resulting in a bad
read (the engineers used the term "thermal asperity" to refer to this
sort of event).

A major reason for the development of bad sectors, is physical damage:
"head slap", in which the head actually hits the platter and knocks
some particles loose.  Thie can happen if the drive or computer is
banged or moved sharply while the drive is spinning, or even when it's
powered off.  If these particles remain on the disk surface (or fly
away and then land again, elsewhere) they're likely to be hit by the
head during a subsequent revolution... which can cause more scraping
or even slapping of the head, more damage to the surface, and the
creation of more loose particles.  Although the drives have a fiber
filter in the air-flow path which is intended to catch these
particles, it's never 100% effective... and so the amount of
contamination builds up as time goes by, and the problem snowballs and
the drive goes downhill towards failure.

After playing around with a number of error-management ideas at TiVo,
I came to the conclusion that it wasn't worth bothering with.  A drive
which shows a significant number of reallocated (or pending-
reallocation) sectors, probably doesn't have very long to live...
its performance will degrade (due to the need to retry reads on
sectors that are going bad) and it will lose more and more data
(unrecoverable errors).  The best filesystem- and application-level
error management techniques I could dream up, wouldn't have extended
the life of a failing drive enough to be worth the effort and
complexity.

--
Dave Platt <dpl...@radagast.org>                                   AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

Thanks for the insight - the physical explanation why this happens
was something I could only have guesses about.
I am mostly using 2.5" drives and DPS (our OS here)
has all the defect detection etc. stuff, done in the early 90-s
(mostly on a SCSI 200 MB 2.5" drive, which was the largest then...
its R/W head must have been still of the inductive type, a little
later drives got much better and larger).
However all that stuff is practically unused since .

Can you say something on the life expectation of drives
which are on most if not all of the time? The SMART data
do have a spin up counter, perhaps this is the main killer,
but I wonder how long the bearing will last with little spin up/
down involved, the number of disks I have had in my hands is
dwarfed by the one your DVR experience suggests.

Dimiter

------------------------------------------------------
Dimiter Popoff Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/

 

[D Yuniskis]

Hi Dimiter,

On 12/21/2010 7:18 PM, Didi wrote:

Can you say something on the life expectation of drives
which are on most if not all of the time? The SMART data
do have a spin up counter, perhaps this is the main killer,
but I wonder how long the bearing will last with little spin up/
down involved, the number of disks I have had in my hands is
dwarfed by the one your DVR experience suggests.

http://labs.google.com/papers/disk_failures.pdf

has some interesting insights

 

[D Yuniskis]

On 12/21/2010 12:18 PM, d_s_klein wrote:

When you build a new file system, this list typically starts at

This makes sense. I'd never considered the issue before.

"empty". One exception is the Windows floppy format - it scans the
disk and builds a new list every time unless you specifically tell it
not to. There are probably options to the other format routines to
force it to build a new list. (I use chkdsk with surface scan
immediately after formatting.) In the 'pre-IDE' days, one got a chart
with the drive, and format was told about the bad sectors "by hand".

Yes, I can remember old MFM drives with such lists. I only ever had
one DEC disk drive -- small (capacity, not size), 128 fixed heads.
I seem to recall it was essentially byte (word) addressable (?)