second hard disk trouble

[Mark Kennedy]

are you saying you ran partition magic v4.X against a 14G drive, and
it saw the entire drive?  when i ran it, it only saw 8G.  when i called
them, they told me it was a BIOS limitation and that they were dependent
on the BIOS for the geometry.  was i taken?  (you can tell i've been living
off the backs of SA's for too long :-).

/mark

Rob Mayoff wrote:
> 
> | PIIX4: IDE controller on PCI bus 00 dev 39
> | PIIX4: not 100% native mode: will probe irqs later
> |     ide0: BM-DMA at 0xfcf0-0xfcf7, BIOS settings: hda:DMA, hdb:pio
> |     ide1: BM-DMA at 0xfcf8-0xfcff, BIOS settings: hdc:DMA, hdd:pio
> | hda: IBM-DYLA-28100, ATA DISK drive
> | hdc: IBM-DCYA-214000, ATA DISK drive
> | ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
> | ide1 at 0x170-0x177,0x376 on irq 15
> | hda: IBM-DYLA-28100, 7815MB w/459kB Cache, CHS=1058/240/63, UDMA
> | hdc: IBM-DCYA-214000, 7559MB w/420kB Cache, CHS=16383/15/63, UDMA
> |
> | I'm not sure if the CHS values are correct, but the size certainly isn't
> | - its smaller than the 8GB drive on the primary! I'm worried that the
> | Heads value is so low - this looks more like the actual value rather
> | than the 'large' value that should maybe be there.
> 
> None of the CHS numbers mean anything about the actual disk geometry
> these days.  The drive hides its true geometry.
> 
> | fdisk (under linux)
> | seems happy to partition it to 7.5GB, but I didn't write it back. Any
> | ideas what I'll need to do to fix this?
> 
> The easiest way by far is simply to use Partition Magic (4.0) to
> partition the disk.  It sees the actual disk geometry.  The Linux kernel
> doesn't care about the purported CHS numbers; it pays attention to the
> partition table.
> 
> If you want to do it the hard way:
> 
> WARNING: I haven't tried this.  I used PM.  However, from reading the
> Large Disk HOWTO and /usr/src/linux/Documentation/ide.txt, I gather that
> this may work.
> 
> Run "hdparm -i /dev/hdc" (as root).  Look for LBAsects.  That should be
> 27609120, which is the actual number of sectors on the disk.  (Each
> sector is 512 bytes; that works out to 14135869440 bytes = ~14.1GB.)
> 
> 27609120 sectors / 63 sectors per head = 438240 heads
> 438240 heads / 240 heads per cylinder = 1826 cylinders
> 
> So you want your disk geometry to be 1826/240/63.  Add this to the
> kernel command line:
> 
>         hdc=1826,240,63
> 
> One slight problem.  I don't know what will happen if you have the CDROM
> (DVDROM) drive installed at boot.
> 
> The 16383/15/63 numbers are reported by the drive to mean "really big".
> Unfortunately, looking at ide.c in my 2.0.36 kernel, I see that Linux
> only recognizes 16383/16/63 as "really big". (Note: 15 != 16.) I don't
> know why the drive reports 16383/15/63 instead. But because of that, and
> because the actual drive size (LBAsects) is more than 10% larger than
> the CHS indicates, Linux assumes that LBAsects is wrong and uses the
> reported CHS.
> 
> I'll probably play with this a bit more after my next full backup.