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What is the difference between a regular Format and a Low Level Format?



 
 
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  #1  
Old November 23rd 17, 12:18 AM posted to microsoft.public.windowsxp.general
No_Name
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Posts: 177
Default What is the difference between a regular Format and a Low Level Format?

What is the difference between a regular Format and a Low Level Format?

I have a program to do Low Level Formats.
I had a flash drive that somehow got screwed up. A regular format did
not fix it, but a low level format got it working again.

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  #2  
Old November 23rd 17, 01:17 AM posted to microsoft.public.windowsxp.general
J. P. Gilliver (John)[_4_]
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Posts: 2,679
Default What is the difference between a regular Format and a Low Level Format?

In message ,
writes:
What is the difference between a regular Format and a Low Level Format?

I have a program to do Low Level Formats.
I had a flash drive that somehow got screwed up. A regular format did
not fix it, but a low level format got it working again.

For disc (partition)s: it used to be that a "quick" format just deletes
the entries in the root directory, thus making the disc (partition) look
as if it has nothing on it (including sub-folders), whereas a full one
actually did some sort of test on every sector, so that dud ones could
be marked as bad and avoided (by in effect making notes of the dud ones
on the disc somewhere). For modern discs where the disc firmware itself
has something that does that, it at least exercises the disc.

I'm not sure if "quick/full" is the same as "regular/low-level".

For a floppy, a full format also in effect wrote something on the disc
that was of use during subsequent operations, rather like drawing lines
on a sheet of paper before you use it; a "low level" format of a hard
disc used to do something similar, but again, in modern HDs that's
probably done before it leaves the manufacturer and isn't really doable
by the user.

For your flash drive, I'm _guessing_ that the quick format - if that's
what you did - just did in effect a "del /s *.*", which wouldn't have
fixed it if the part that stored the root directory was corrupted,
whereas the low-level format would have re-initialised it.

But someone - Paul probably - will be along in a moment to say more than
just my guesses (-:.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

Reality television. It's eroding the ability of good scripted television to
survive. - Patrick Duffy in Radio Times 2-8 February 2013
  #3  
Old November 23rd 17, 02:24 AM posted to microsoft.public.windowsxp.general
Paul[_32_]
external usenet poster
 
Posts: 11,873
Default What is the difference between a regular Format and a Low LevelFormat?

wrote:
What is the difference between a regular Format and a Low Level Format?

I have a program to do Low Level Formats.
I had a flash drive that somehow got screwed up. A regular format did
not fix it, but a low level format got it working again.


A partition "Quick Format" assigns a file system to a partition.
It has nothing to do with the workings of the disk drive itself.
A Quick Format writes a FAT or $MFT, writes a file system
header, and that's it. It doesn't check anything.

A partition "Format" without the quick, does a read verify of
every cluster after the same steps as the previous paragraph.
If bad clusters are found, they're added to the $BADCLUS list.
The intention is, with a regular format, to "block" any
bad sectors so they cannot be used. A bad sector is
defined as a sector returning a CRC error, where the
automatic sparing can no longer repair it and keep
the sector in service.

*******

A "low level" format is a disk drive technology, It has
nothing to do with partitions or even OSes. It's something
that happens at the platter level.

Modern drives have a servo pattern recorded at the factory.
The drive is only allowed to write to data sector areas.
So all that a modern drive can do, is "zero" out the data.
It's not allowed to change any other aspects of data content.
As a result, there is no "low level" format on a modern drive.
Even if a command existed in the ATA/ATAPI command set for
it, only the data sector portion could be written.

On an "old" drive, both the sector head and sector data
areas are candidates for writes. During a normal write
operation, only the sector data is written. During
a "low level" format, both the sector head and the
sector data are refreshed. And back in those days,
if you interrupted the "low level" format, the
disk tended to be ruined. When really you should
have been able to start the process over again. It suggests
at the end of the low level format, some info must have
been written to the "critical data" section of the
platter at "track -1". That's also the area where the
drive firmware is kept (when you flash a drive, track -1
gets the information stored there).

A "low level" format can be beneficial to a flaky "old"
drive, but you must not interrupt the process - even
if the software looks like it's frozen :-/ Been there,
and done that.

Paul
  #4  
Old November 23rd 17, 10:27 AM posted to microsoft.public.windowsxp.general
Ian Jackson[_4_]
external usenet poster
 
Posts: 75
Default What is the difference between a regular Format and a Low Level Format?

In message , Paul
writes
wrote:
What is the difference between a regular Format and a Low Level Format?
I have a program to do Low Level Formats. I had a flash drive that
somehow got screwed up. A regular format did
not fix it, but a low level format got it working again.


A partition "Quick Format" assigns a file system to a partition.
It has nothing to do with the workings of the disk drive itself.
A Quick Format writes a FAT or $MFT, writes a file system
header, and that's it. It doesn't check anything.

A partition "Format" without the quick, does a read verify of
every cluster after the same steps as the previous paragraph.
If bad clusters are found, they're added to the $BADCLUS list.
The intention is, with a regular format, to "block" any
bad sectors so they cannot be used. A bad sector is
defined as a sector returning a CRC error, where the
automatic sparing can no longer repair it and keep
the sector in service.

*******

A "low level" format is a disk drive technology, It has
nothing to do with partitions or even OSes. It's something
that happens at the platter level.

Modern drives have a servo pattern recorded at the factory.
The drive is only allowed to write to data sector areas.
So all that a modern drive can do, is "zero" out the data.
It's not allowed to change any other aspects of data content.
As a result, there is no "low level" format on a modern drive.
Even if a command existed in the ATA/ATAPI command set for
it, only the data sector portion could be written.

On an "old" drive, both the sector head and sector data
areas are candidates for writes. During a normal write
operation, only the sector data is written. During
a "low level" format, both the sector head and the
sector data are refreshed. And back in those days,
if you interrupted the "low level" format, the
disk tended to be ruined. When really you should
have been able to start the process over again. It suggests
at the end of the low level format, some info must have
been written to the "critical data" section of the
platter at "track -1". That's also the area where the
drive firmware is kept (when you flash a drive, track -1
gets the information stored there).

A "low level" format can be beneficial to a flaky "old"
drive, but you must not interrupt the process - even
if the software looks like it's frozen :-/ Been there,
and done that.

Paul


In the past few years, I've collected a load old/ancient disks, and used
some of them to 'keep my hand in' doing XP installs on an old clunker
PC. [These never seem to go the same way twice, but that's another
story.]

X-GSmartControl (and other tests) shows that quite a lot of these disks
have a few minor historical errors, so I decided that it might be a good
idea to do a low-level format on some of them (using HDD LLF Low Level
Format Tool). This didn't seem to do any harm to the disks, but on one
type (IIRC, all 160GB Seagate), when I tried to install XP, when it got
to removing the installation disk and rebooting, the reboot came up with
a blue screen showing the message "Unmountable boot volume" (and a lot
more). IIRC, three Seagate disks did the exactly the same, but a couple
of others (Maxtor 40GB, I think) were OK.

So is this just a coincidence, or can a low-level format leave at least
certain types of hard drives looking apparently OK - but unusable for
installing an operating system on?
--
Ian
  #5  
Old November 23rd 17, 11:25 AM posted to microsoft.public.windowsxp.general
Paul[_32_]
external usenet poster
 
Posts: 11,873
Default What is the difference between a regular Format and a Low LevelFormat?

Ian Jackson wrote:


In the past few years, I've collected a load old/ancient disks, and used
some of them to 'keep my hand in' doing XP installs on an old clunker
PC. [These never seem to go the same way twice, but that's another story.]

X-GSmartControl (and other tests) shows that quite a lot of these disks
have a few minor historical errors, so I decided that it might be a good
idea to do a low-level format on some of them (using HDD LLF Low Level
Format Tool). This didn't seem to do any harm to the disks, but on one
type (IIRC, all 160GB Seagate), when I tried to install XP, when it got
to removing the installation disk and rebooting, the reboot came up with
a blue screen showing the message "Unmountable boot volume" (and a lot
more). IIRC, three Seagate disks did the exactly the same, but a couple
of others (Maxtor 40GB, I think) were OK.

So is this just a coincidence, or can a low-level format leave at least
certain types of hard drives looking apparently OK - but unusable for
installing an operating system on?


That sounds like a 48 bit LBA problem (cuts in at 137GB, 120GB
drives OK, 160GB IDE drives could deliver a surprise). That's a problem
on IDE drives, before ATA/ATAPI 6 or so. Seagate offered a document
on the topic, which is a place to start, but not the end of the
story. Some of the pronouncements in here are overly pessimistic.

http://web.archive.org/web/200701210...c/tp/137gb.pdf

Older IDE hardware, before 2003, supports 28-bit LBA, and that
causes a limitation in practical partition size. If the address
rolls over in hardware, an attempt to write to the 137GB mark,
ends up writing to location zero, wiping out the file
system header or other valuable goods.

After 2003, more BIOS and hardwares were claimed to support
48-bit LBA, which significantly extends the address space.
There was an announcement by one of the motherboard companies,
that all their stuff supported 48-bit on IDE, after a certain
magic date. I think it was 2003, but my memory isn't very good.

The original proposal to the standards body, on how to do this,
is documented here (the year 2004 is the first time Archive.org
took a snapshot). It was a "double-pumping" of some registers,
to cause fewer interface changes or something. On page two, it
shows how an extended set of information, is loaded, via the
pattern in the upper table. That's how they fit 48-bits.

https://web.archive.org/web/20041024...l/e00101r6.pdf

I thought the behavior of Windows handled this pretty well.
I'm surprised the boot was a problem. For example, Win2K SP2
won't make a partition larger than 137GB on a 160GB disk,
so it won't get into trouble. (That's because Win2K SP2 can
also corrupt a larger hard drive, given a chance. Win2K SP2
was doing the best job it knew how to do.) But if a second partition
happens to span the 137GB mark, that could easily cause
corruption. You can "import" a drive from a more modern OS,
and have it ruined by Win2K SP2 (SP4 is OK).

x 137GB
-------------------------------------------------------------
Partition below 137GB Partition spanning 137GB = trouble
is OK and works by itself |
|
^ | A write to 137GB, goes down to zero,
+-------------------------------+ corrupting the first partition or MBR

*******

Using another OS drive, boot the system and do your forensics
on the 160GB drives that aren't behaving themselves. It could
be that the OS partition is completely trashed. See if you
can spot the "NTFS" string in the first sector of the
partition for example. A copy of HXD could help, as it has
an option to open a hard drive for low-level access. You will
have to take your best shot at the math to work out where
the partition(s) start and end. I like PTEDIT32 for this
purpose - it's a great help, and it was easily available up
until a year or two ago.

https://mh-nexus.de/en/hxd/

*******

If you want to "cheat death" and you have the time to spend,
try pre-formatting the 160GB drive. Say, make a 100GB partition
and format it NTFS. Now, put it in the system where you'll be
doing the install. Tell the installer to install in the
100GB partition (not above that). When you boot, it should work.
Don't allow the installer to pick its own size (it indeed, that's
how this mess was caused). Maybe you were using a WinXP Gold year 2002
or so CD ?

Paul
  #6  
Old November 24th 17, 05:32 PM posted to microsoft.public.windowsxp.general
Ian Jackson[_4_]
external usenet poster
 
Posts: 75
Default What is the difference between a regular Format and a Low Level Format?

In message , Paul
writes
Ian Jackson wrote:





So is this just a coincidence, or can a low-level format leave at
least certain types of hard drives looking apparently OK - but
unusable for installing an operating system on?


That sounds like a 48 bit LBA problem (cuts in at 137GB, 120GB
drives OK, 160GB IDE drives could deliver a surprise). That's a problem
on IDE drives, before ATA/ATAPI 6 or so. Seagate offered a document
on the topic, which is a place to start, but not the end of the
story. Some of the pronouncements in here are overly pessimistic.

http://web.archive.org/web/200701210...te.com/support
/kb/disc/tp/137gb.pdf

Older IDE hardware, before 2003, supports 28-bit LBA, and that
causes a limitation in practical partition size. If the address
rolls over in hardware, an attempt to write to the 137GB mark,
ends up writing to location zero, wiping out the file
system header or other valuable goods.

After 2003, more BIOS and hardwares were claimed to support
48-bit LBA, which significantly extends the address space.
There was an announcement by one of the motherboard companies,
that all their stuff supported 48-bit on IDE, after a certain
magic date. I think it was 2003, but my memory isn't very good.

The original proposal to the standards body, on how to do this,
is documented here (the year 2004 is the first time Archive.org
took a snapshot). It was a "double-pumping" of some registers,
to cause fewer interface changes or something. On page two, it
shows how an extended set of information, is loaded, via the
pattern in the upper table. That's how they fit 48-bits.

https://web.archive.org/web/20041024...10.org:80/t13/
technical/e00101r6.pdf

I thought the behavior of Windows handled this pretty well.
I'm surprised the boot was a problem. For example, Win2K SP2
won't make a partition larger than 137GB on a 160GB disk,
so it won't get into trouble. (That's because Win2K SP2 can
also corrupt a larger hard drive, given a chance. Win2K SP2
was doing the best job it knew how to do.) But if a second partition
happens to span the 137GB mark, that could easily cause
corruption. You can "import" a drive from a more modern OS,
and have it ruined by Win2K SP2 (SP4 is OK).

x 137GB
-------------------------------------------------------------
Partition below 137GB Partition spanning 137GB = trouble
is OK and works by itself |
|
^ | A write to 137GB, goes down to zero,
+-------------------------------+ corrupting the first partition or MBR

*******

Using another OS drive, boot the system and do your forensics
on the 160GB drives that aren't behaving themselves. It could
be that the OS partition is completely trashed. See if you
can spot the "NTFS" string in the first sector of the
partition for example. A copy of HXD could help, as it has
an option to open a hard drive for low-level access. You will
have to take your best shot at the math to work out where
the partition(s) start and end. I like PTEDIT32 for this
purpose - it's a great help, and it was easily available up
until a year or two ago.

https://mh-nexus.de/en/hxd/

*******

If you want to "cheat death" and you have the time to spend,
try pre-formatting the 160GB drive. Say, make a 100GB partition
and format it NTFS. Now, put it in the system where you'll be
doing the install. Tell the installer to install in the
100GB partition (not above that). When you boot, it should work.
Don't allow the installer to pick its own size (it indeed, that's
how this mess was caused). Maybe you were using a WinXP Gold year 2002
or so CD ?

Paul


Thanks for the comprehensive follow-up. I'm looking into the 137GB
limit.

The PC has an Asus motherboard (can't remember the model at the moment),
and dates from 2001 or 2. The OS is XP Home, and I see that XP Home
Service Pack 1 (SP1) or higher should be OK with 137G. [I've also tried
a different installation disk which includes SP2, and had the same
problem.]

As the installation disk includes SP1, am I right to assume that this
all gets installed before the reboot? If not, and only the basic XP gets
installed initially, that might explain the problem. [It's quite some
time since I did this (I see that I already raised the problem in
January - but didn't go into as much detail about the disk sizes), so I
can't remember if you replace the same disk after the reboot.]

However, as you suggest, I'll try splitting the 160GB drive so that the
first partition is less than 137GB, and see if that will accept an
installation. I can also try cloning the present 137GB disk (it's
either 40 or 80GB) to the 160GB disk (although I have a feeling that
I've already tried that, but can't remember what happened).
--
Ian
  #7  
Old November 24th 17, 09:18 PM posted to microsoft.public.windowsxp.general
Ian Jackson[_4_]
external usenet poster
 
Posts: 75
Default What is the difference between a regular Format and a Low Level Format?

In message , Ian Jackson
writes
In message , Paul
writes
Ian Jackson wrote:








However, as you suggest, I'll try splitting the 160GB drive so that the
first partition is less than 137GB, and see if that will accept an
installation. I can also try cloning the present 137GB disk (it's
either 40 or 80GB) to the 160GB disk (although I have a feeling that
I've already tried that, but can't remember what happened).


Just an addendum.....
I think I've already installed XP Home and XP Pro on several disks that
were 160GB (and even more) - and also cloned to them. I therefore feel
it's unlikely that the problem is a possible 137GB limit, but instead is
that the low-level format has done something to them. However, I will
try them again.
--
Ian
 




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