Disk geometry, 5.3b7 install

[Subhro]

On Thu, 14 Oct 2004 00:48:34 -0600, freebsd at dreamchaser.org 

> When I boot off a CD (image created from downloaded iso image),
> start the install, and go to allocate the freebsd slice, it reports
>   155061/16/63  ad4
> and says the geometry is invalid
> 

What does the sticker on top of the drive say about its geometry. I
would like to explicitly instruct fdisk to use the Geometry on the
sticker but only if fdisk or anyone else complains during the install.

> If I go ahead and attempt to partition, I see
> Geometry ad4 9729 cylinders/255 heads/63 sectors = 156296385 sectors
>                                                    (76316MB)
>   Offset   Size(St)    End      Name  PType  Desc      SubType  Flags
>        0         63         62   --    12   unused         0
>       63   16386237   16386299  ad4s1   4   NTFS/HPFS/QNX  7
> 16386300  139915188  156301487   --    12   unused         0
> 

This one is fine. Whats the problem? You can just make up the slice
from the unsed free space starting from offset 16386300.

> F1 help suggests running tools/pfdisk, for which there appears to be
> no documentation, but which appears to be a very old tool applicable
> only to disks smaller than 8G and not using LBA.

Nopes thats not right. It does apply to the modern drives well.

> 
> Questions:
> 
> 1.  Is the geometry (155061/16/63) really invalid?
>     Given the 1024 cyl limitation, it doesn't look to me like the
>     modified geometry (9729/255/63) assumed? by fdisk is any better,
>     since both 155061 and 9729 are > 1024.
>     In any case, the drive uses LBA, so why is this an issue and
>     even being reported?

Well, I already answered the first part. Regarding the reporting,
there can be many reasons why it is reaported. One of the most common
reason is that, the BIOS does not allow LBA transparently. Also
FreeBSD had the reputation (or should I say ill reputation?) of
getting information directly from the hardware and nopt rely on BIOS
whenever it can.

> 2.  Do I really want to reset it?  Is that even relevant when LBA
>     is being used?

I would reset it only if someone complains during install.

> 3.  Is pfdisk and geometry even relevant for disks > 8G?
> 
As far as I know it is.

> Thanks for any insights,

You are welcome

Regards
S.

-- 
Subhro Sankha Kar
School of Information Technology
Block AQ-13/1 Sector V
ZIP 700091
India