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Large Disk HOWTO

Andries Brouwer, aeb@cwi.nl

v2.2x, 30 Aug 2001

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All about disk geometry and the 1024 cylinder limit for disks.

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For the most recent version of this text, see www.win.tue.nl .

1. The problem

2. Summary

3. Units and Sizes

• 3.1 Sectorsize
• 3.2 Disksize

4. Disk Access

• 4.1 BIOS Disk Access and the 1024 cylinder limit
• 4.2 History of BIOS and IDE limits

5. Booting

• 5.1 LILO and the `lba32' and `linear' options
• 5.2 A LILO bug
• 5.3 1024 cylinders is not 1024 cylinders
• 5.4 No 1024 cylinder limit on old machines with IDE

6. Disk geometry, partitions and `overlap'

• 6.1 The last cylinder
• 6.2 Cylinder boundaries

7. Translation and Disk Managers

8. Kernel disk translation for IDE disks

• 8.1 EZD
• 8.2 DM6:DDO
• 8.3 DM6:AUX
• 8.4 DM6:MBR
• 8.5 PTBL
• 8.6 Getting rid of a disk manager

9. Consequences

• 9.1 Computing LILO parameters

10. Details

• 10.1 IDE details - the seven geometries
• 10.2 SCSI details

11. The Linux IDE 8 GiB limit

• 11.1 BIOS complications
• 11.2 Jumpers that select the number of heads
• 11.3 Jumpers that clip total capacity

12. The Linux 65535 cylinder limit

• 12.1 IDE problems with 34+ GB disks

13. Extended and logical partitions

14. Problem solving

• 14.1 Problem: My IDE disk gets a bad geometry when I boot from SCSI.
• 14.2 Nonproblem: Identical disks have different geometry?
• 14.3 Nonproblem: fdisk sees much more room than df?

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