Disk geometry changed after running linux

Disk geometry changed after running linux

[David Balazic]

I encountered a weird problem.

My HW :
MSI K7T Pro2 motherboard ( VIA KT133 chipset ,
 VT82C686A south bridge )
primary master IDE : Quantum Fireball lct20 , ATA-100 , 20 GB
secondary master : Teac CD532E-B

AWARD BIOS settings :
PM : type : AUTO , Access mode : AUTO
SM : type : AUTO , Access mode : AUTO
PS/SS: NONE/NONE

PM disk was set to LBA access mode on each boot.
I had one primary and one logical NTFS partition.


Then I installed linux ( "some" beta version , kernel
is some recent 2.4.0-testXX )

I didn't install any LILO boot sectors , but created a boot-floppy.

After the installation the disk ( win2000 ) would not boot.
It reports :
Read error on disk.
Press ctrl+alt+del to reboot.

If I run linux ( it work OK from the boot floppy ),
it reports the geometry as 3xxxx/??/??.
Thirty thousand and some cylinders , H and S are probably 16/63
( don't have it at hand ).

It should be two thousand something and 255/63, I think.

fdisk -l /dev/hda prints "Partition 1 does not end on cylinder boundary"
messages for the NTFS partitions ( hda1 and hda5 ). The linux ones are
OK.

The problem is that now the BIOS sets Access mode to LARGE.
I can workaround it by changing access mode in BIOS setup
from AUTO to LBA, but I want to know what made BIOS to default to
LARGE and how to fix it.

-- 
David Balazic
--------------
"Be excellent to each other." - Bill & Ted
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Re: Disk geometry changed after running linux

[Guest section DW]

On Mon, Jan 15, 2001 at 07:18:30PM +0100, David Balazic wrote:

> Then I installed linux ( "some" beta version , kernel
> is some recent 2.4.0-testXX )
> 
> After the installation the disk ( win2000 ) would not boot.
> It reports :
> Read error on disk.
> Press ctrl+alt+del to reboot.
> 
> If I run linux ( it work OK from the boot floppy ),
> it reports the geometry as 3xxxx/??/??.
> Thirty thousand and some cylinders , H and S are probably 16/63
> ( don't have it at hand ).
> 
> It should be two thousand something and 255/63, I think.
> 
> fdisk -l /dev/hda prints "Partition 1 does not end on cylinder boundary"
> messages for the NTFS partitions ( hda1 and hda5 ). The linux ones are
> OK.
> 
> The problem is that now the BIOS sets Access mode to LARGE.
> I can workaround it by changing access mode in BIOS setup
> from AUTO to LBA, but I want to know what made BIOS to default to
> LARGE and how to fix it.

Since "disk geometry" has become such a terrible mess,
recent BIOSes decide that they don't know what the geometry
should be, and guess the geometry from the partition table,
if there is one.

So, if you added partitions during the install then it is
not impossible that the BIOS changed its mind concerning
the geometry.

It would be interesting to see the precise partition table
(output of "fdisk -l /dev/hda").


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Re: Disk geometry changed after running linux

[David Balazic]

Guest section DW wrote:
> 
> On Mon, Jan 15, 2001 at 07:18:30PM +0100, David Balazic wrote:
> 
> > Then I installed linux ( "some" beta version , kernel
> > is some recent 2.4.0-testXX )
> >
> > After the installation the disk ( win2000 ) would not boot.
> > It reports :
> > Read error on disk.
> > Press ctrl+alt+del to reboot.
> >
> > If I run linux ( it work OK from the boot floppy ),
> > it reports the geometry as 3xxxx/??/??.
> > Thirty thousand and some cylinders , H and S are probably 16/63
> > ( don't have it at hand ).
> >
> > It should be two thousand something and 255/63, I think.
> >
> > fdisk -l /dev/hda prints "Partition 1 does not end on cylinder boundary"
> > messages for the NTFS partitions ( hda1 and hda5 ). The linux ones are
> > OK.
> >
> > The problem is that now the BIOS sets Access mode to LARGE.
> > I can workaround it by changing access mode in BIOS setup
> > from AUTO to LBA, but I want to know what made BIOS to default to
> > LARGE and how to fix it.
> 
> Since "disk geometry" has become such a terrible mess,
> recent BIOSes decide that they don't know what the geometry
> should be, and guess the geometry from the partition table,
> if there is one.
> 
> So, if you added partitions during the install then it is
> not impossible that the BIOS changed its mind concerning
> the geometry.
> 
> It would be interesting to see the precise partition table
> (output of "fdisk -l /dev/hda").

Sorry , can't get it until saturday :-(

fdisk reports the disk geometry as 3xxxxx/xx/xx which probably LARGE.
I don't remember the start/stop cylinders of partitions.

Is there a way to change the geometry from fdisk ?
I tried expert mode and 'set sectors' and 'set heads',
but after I exit fdisk with 'w' , it is unchanged.


-- 
David Balazic
--------------
"Be excellent to each other." - Bill & Ted
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Re: Disk geometry changed after running linux

[Guest section DW]

On Mon, Jan 15, 2001 at 07:54:47PM +0100, David Balazic wrote:

> Is there a way to change the geometry from fdisk ?
> I tried expert mode and 'set sectors' and 'set heads',
> but after I exit fdisk with 'w' , it is unchanged.

As you know, a disk does not have a geometry, but
the location of a partition is described in linear
and 3D coordinates, and translating between the two
requires a geometry. Commands like
	% sfdisk -d /dev/hdf > hdf.pt
	% sfdisk /dev/hdf < hdf.pt
suffice to make the translation uniform for the
kernel's current idea of sectors, heads.
If you don't like that idea, then -C,-H,-S options
serve to tell sfdisk about the desired geometry.
See sfdisk(8).
[Save a copy of the old situation, and make the geometry so
that Windows likes it. Linux is happy with every geometry.]

Andries

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