Re: Why check legacy partition table for non-legacy HDs?

[Pixel]

"H. J. Lu" <address@hidden> writes:

> My question why parted even bothers with number of cylinders > 1024
> for legacy stuff. Linux's fdisk doesn't. Here is a patch.

talking about legacy, I encounter more and more pbs "Total allocated
sectors %d greater than the maximum %d" because the size of a hard
drive is not always a multiple of the number of Cylinders (see below)

In diskdrake, i'm considering adjusting the end of the last partition
on the last cylinder for compatibility with legacy tools (fdisk,
pqmagic). fdisk could be enhanced to handle this, but pqmagic... :-(

Comments?
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        Cylinder/Head/Size Hell Is Not Over 

            address@hidden 
         $Date: 2002/08/20 12:13:41 $


Nowadays, you can boot Linux without ever relying on CHS
(Cylinder/Head/Size):

- CHS information on partition table is obsolete and not used anymore.
It was causing the 1024th cylinder limitation:
  - disallowing partitions above 8GiG. Problem overcome using 28bits Linear
  Block Addressing (LBA) in partition table.
  - disallowing to boot on partition above 8GiG (due to int13 limitation used
  in bootloaders). Problem overcome using int13 extensions (EDD)

Logical CHS (Cylinder/Head/Size) and physical CHS are not related anymore.
Especially the size of a hard drive is not a multiple of the number of
Cylinders.


The problem is that many tools still rely somewhat heavily on CHS information.
- most tools adjust partitions on cylinder boundary
- some tools compute the size of the disk based on CHS (eg: fdisk)


Resulting problems in various tools:

- last partition not cylinder boundary adjusted, and overrun CHS computed size
  - fdisk
    > Total allocated sectors %d greater than the maximum %d
  - cfdisk (need confirmation)
    > FATAL ERROR: Bad primary partition %d: Partition ends after end-of-disk
    or
    > FATAL ERROR: Bad logical partition %d: Partition ends after end-of-disk
  - Partition Magic (version?)
    > Error #109: Partition ends after end of disk
  - Windows <= 98se, Windows Me
    (doesn't like it, what error message?)

  Tools handling it correctly:
  - parted and so diskdruid in RedHat >= 7.2 (or is it 7.x?)
  - diskdrake >= Mandrake 8.2
  - Windows XP (need confirmation)

  Tools using the full size of the disk, and so causing pbs with 
fdisk/cfdisk/...:
  - diskdrake >= Mandrake 8.2
  - parted (what about diskdruid??)

- disagreement between CHS and linear address
  - parted
    > "Warning: Unable to align partition properly.  This probably means that
    > another partitioning tool generated an
    > incorrect partition table, because it didn't have the correct BIOS
    > geometry.  It is safe to ignore,but
    > ignoring may cause (fixable) problems with some boot loaders.
    > Ignore Cancel ? C
  - lilo
    > Warning: Kernel & BIOS return differing head/sector geometries for device 
0x80
    >     Kernel: 38792 cylinders, 16 heads, 63 sectors
    >       BIOS: 1023 cylinders, 255 heads, 63 sectors
    > Device 0x2100: Inconsistent partition table, 2nd entry
    >   CHS address in PT:  48:0:1  -->  LBA (771120)
    >   LBA address in PT:  48384  -->  CHS (3:3:1)
    > The partition table is *NOT* being adjusted.

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