OT: bad sector remapping

[D Yuniskis]

On 12/21/2010 12:22 PM, d_s_klein wrote:

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.

There *never* will be anything to "recover" on it. I don't use
laptops for anything other than "small GUI's". A friend will
be using this one to access email, browse the web and view
pictures from digital camera. I.e., all things that exist *outside*
the PC's disk.

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

I volunteer at a recycling facility. This attitude is far too
common. "Recycled" machines (at most such places) I *scrapped*
for precious metals, etc. A huge waste of resources for something
that is typically still "serviceable" (it is not uncommon for
an 18-wheeler to pull up FULL of PC's to be recycled -- just because
some business decided that it's been 18 months since they last
purchased machines... :-/ ). Unfortunately, it takes a lot of
labor to reintroduce a machine into normal use once it has gone
this route. But, schools, charities, etc. sure appreciate NOT
having to pay for them!

I would prefer not to be a part of that problem.

 

Robert Roland wrote:

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.

Modern drives can't be low level formatted by the user, but not
because of the servo, which is written between the sectors or more
deeply than the other information. One early drive with an embedded
servo was the Toshiba MK-72x, an ST506/412 interface drive with 10
heads and 5 platters, and it could definitely be low level formatted.

 

[Meat Plow]

On Tue, 21 Dec 2010 19:48:13 -0700, D Yuniskis wrote:

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 (?)

First HD I owned was a Kalok 330 RLL. I think it was around 30 megabytes.
The DEBUG command was used to low level format these and MFM drives.
Usually on an AT/XT PC it was > debug.com then G=C800:5.

Do you go back that far?



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

 

[Jim Stewart]

Meat Plow wrote:

First HD I owned was a Kalok 330 RLL. I think it was around 30 megabytes.
The DEBUG command was used to low level format these and MFM drives.
Usually on an AT/XT PC it was> debug.com then G=C800:5.

Do you go back that far?

I've rewritten timing tracks on DEC DF32
and RF08 head-per-track drives when you
were in grade school.

 

[Meat Plow]

On Wed, 22 Dec 2010 10:46:28 -0800, Jim Stewart wrote:

Meat Plow wrote:

First HD I owned was a Kalok 330 RLL. I think it was around 30
megabytes. The DEBUG command was used to low level format these and MFM
drives. Usually on an AT/XT PC it was> debug.com then G=C800:5.

Do you go back that far?

I've rewritten timing tracks on DEC DF32 and RF08 head-per-track drives
when you were in grade school.

So is this "MY COCK IS BIGGER THAN YOURS" contest for you or do you
really think I give a fuck what you did or when you did it.

BTW I was is high school back when you were fiddling wither your DIC.





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

 

[David Nebenzahl]

On 12/22/2010 11:01 AM Meat Plow spake thus:

On Wed, 22 Dec 2010 10:46:28 -0800, Jim Stewart wrote:

Meat Plow wrote:

First HD I owned was a Kalok 330 RLL. I think it was around 30
megabytes. The DEBUG command was used to low level format these
and MFM drives. Usually on an AT/XT PC it was> debug.com then
G=C800:5.

Do you go back that far?

I've rewritten timing tracks on DEC DF32 and RF08 head-per-track drives
when you were in grade school.

So is this "MY COCK IS BIGGER THAN YOURS" contest for you or do you
really think I give a fuck what you did or when you did it.

BTW I was is high school back when you were fiddling wither your DIC.

Ah, Meat Head shows his good manners again ...


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

 

[Meat Plow]

On Wed, 22 Dec 2010 17:34:46 -0800, David Nebenzahl wrote:

On 12/22/2010 11:01 AM Meat Plow spake thus:

On Wed, 22 Dec 2010 10:46:28 -0800, Jim Stewart wrote:

Meat Plow wrote:

First HD I owned was a Kalok 330 RLL. I think it was around 30
megabytes. The DEBUG command was used to low level format these and
MFM drives. Usually on an AT/XT PC it was> debug.com then G=C800:5.

Do you go back that far?

I've rewritten timing tracks on DEC DF32 and RF08 head-per-track
drives when you were in grade school.

So is this "MY COCK IS BIGGER THAN YOURS" contest for you or do you
really think I give a fuck what you did or when you did it.

BTW I was is high school back when you were fiddling wither your DIC.

Ah, Meat Head shows his good manners again ...

The Revenge Dweeb chimes in right on cue. I never claimed to have good
manners you simpering fuckwit. Don't like what I post, don't read it.



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

 

[Franc Zabkar]

On Tue, 21 Dec 2010 11:39:01 -0700, D Yuniskis
<not.going.to.be@seen.com> put finger to keyboard and composed:

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)

The drive will wait for a Write command from the host (ie the OS)
before it processes a "pending" sector. When a write command is
issued, the drive retests the pending sector and returns it to service
if good, or reallocates the LBA to a spare sector if bad.

If CHKDSK finds a bad sector, then it takes it out of service and adds
it to the $BADCLUS metafile in the case of NTFS, or marks it as bad in
the File Allocation Table in the case of FAT16 or FAT32. Thereafter
the sector is never accessed again until the next time the drive is
formatted. In fact my own Seagate drive had 1 pending sector for its
entire life because Windows 98's Scandisk had marked it as bad.

In short, the list of bad clusters maintained by the OS, and the lists
of grown and factory defects (G-list and P-list) maintained by the
drive, are essentially unrelated. In fact, once a sector has made it
into into the G-list, it becomes invisible to the OS. All that the OS
sees is an LBA (Logical Block Address), not a physical sector.
Remapping or reallocation is the process by which the drive
transparently takes a sector from a pool of spares and assigns it to a
particular unreadable LBA. The host is never aware that this has
happened.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[Franc Zabkar]

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

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).

Use a comprehensive SMART diagnostic tool. Look for reallocated,
pending, or uncorrectable sectors.

HD Sentinel (DOS / Windows / Linux):
http://www.hdsentinel.com/

HDDScan for Windows:
http://hddscan.com/

See this article for SMART info:
http://en.wikipedia.org/wiki/S.M.A.R.T.

MHDD can also display the SMART data.

A "low level format" on modern drives merely writes zeros to each
sector. It doesn't actually perform a real LLF. After zeroing the
drive, any "pending" sectors will be transparently retested and
reallocated with spares, if necessary.


- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.