[RndTbl] drive partitioning for Linux install

Dan Martin ummar143 at cc.umanitoba.ca
Fri Sep 30 17:50:04 CDT 2005


Thanks a bunch!  That's exactly what the problem is.  Soime time ago I 
changed my IDE connections, but neglected to change the BIOS.  hda used 
LBA addressing, but hdc used AUTO, which defaulted to CHS.  This 
explains some of life's mysteries, like why 2 identical drives appear 

I will have to look at partitions on my P4, since the BIOS is set to 
AUTO for those, and the drives have both DOS and Linux partitions.  I 
hope those partition tables are consistent.

I assume the need for LBA settings is relevant only if
1) using DOS, or,
2) using LILO
since Linux does not depend on the BIOS addressing.

Is there ever a good reason to NOT use LBA? [perhaps installing an 
ancient drive with stuff on it partitioned under an old scheme?]  In 
theory, files could be arranged by cylinder to minimize seek times, but 
in fact the CHS geometries are not "real" anyways, so no benefit there.

Thanks again.

Adam Thompson wrote:

> Short answer:   turn on LBA support in your BIOS.  Don't use 'auto' or 
> 'large drive support', if you can avoid it, and especially avoid 'chs' 
> settings.
> That may not be sufficient, it depends on what version of DOS you're 
> running.
> Unfortunately, if you turn on LBA (or LBA32) mode, your partition 
> table will be scrambled... but even worse, if you boot from DOS it 
> will still read sector 0 from the drive and infer geometry from what 
> it finds there, not from the BIOS.  The easiest way around this is to 
> turn on LBA, then immediately install Windows 2000 or Windows XP or 
> Linux.  Don't even try booting DOS until you've successfully recreated 
> the partition table under a more advanced OS.  Do NOT try "fixing" 
> things with PartitionMagic at this point, it will just make a worse mess.
> (If you boot a Linux kernel, during the boot sequence it identified 
> the disks it found.  Output from 'dmesg' should indicate "hda: ....." 
> and it should show some sort of indication as to whether the disk 
> geometry is in C/H/S mode or LBA mode.)
> You might want to read the Large Disk HOWTO, found at:  
> http://www.tldp.org/HOWTO/Large-Disk-HOWTO.html as it discusses the 
> sort of thing that I think you're running into.
> -Adam


Dr. Dan Martin, MD, CCFP, BSc, BCSc (Hon)

GP Hospital Practitioner
Computer Science grad student
ummar143 at cc.umanitoba.ca
(204) 831-1746
answering machine always on

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