large disk with DOS?

large disk with DOS?

Post by Alan Jon » Thu, 27 Jan 2000 04:00:00



I have read the Large Disk How To.  Why does it advise caution when
sharing a large disk with DOS?  I have an IBM 13.5G HD instaled in an
Abit BP6 based computer, IDE1.  The BP6 BIOS is is set for LBA mode
and shows 1650 Cylinders, 255 heads, 63 sectors.  I have managed to
patition it with a modest DOS 6.22 patition,  Fat 32 (empty Win98),
and  Linux primary partitions, and an extended partition with a linux
swap partition.  I have Dos and Win 3.1 installed, but I have used it.
I have Mandrake 6.0 installed in the Linux partition.  I have an old
small drive on IDE0 with DOS 6.22 and Win3.1, and LILO.  I currently
boot into DOS on the old drive or Linux on the large drive.  I want to
run DOS and use a generous amount of fat 16 file archive space on the
large drive.  I understand that DOS cannot access more than about 8.4G
of the drive, but is it safe to use DOS within that limit and share
the drive with Linux?  I plan to move the drive to IDE2, the HPT
controller, as soon as a new distribution is available with Linux 2.4.


 
 
 

large disk with DOS?

Post by John in » Sat, 29 Jan 2000 04:00:00


Alan,

Both DOS and Linux are limited at boot time to the first 1024
cylinders of any disk.  DOS always has this limitation, since it uses
the BIOS for disk access.  Linux does not have this limitation AFTER
it is booted.

The Linux LILO boot limitation is removed by version 22 (still in beta
release).  The source is at:   ftp://sd.dynhost.com/pub/linux/lilo.

DOS will always have the 1024 cylinder limitation.

--John


>I have read the Large Disk How To.  Why does it advise caution when
>sharing a large disk with DOS?  I have an IBM 13.5G HD instaled in an
>Abit BP6 based computer, IDE1.  The BP6 BIOS is is set for LBA mode
>and shows 1650 Cylinders, 255 heads, 63 sectors.  I have managed to
>patition it with a modest DOS 6.22 patition,  Fat 32 (empty Win98),
>and  Linux primary partitions, and an extended partition with a linux
>swap partition.  I have Dos and Win 3.1 installed, but I have used it.
>I have Mandrake 6.0 installed in the Linux partition.  I have an old
>small drive on IDE0 with DOS 6.22 and Win3.1, and LILO.  I currently
>boot into DOS on the old drive or Linux on the large drive.  I want to
>run DOS and use a generous amount of fat 16 file archive space on the
>large drive.  I understand that DOS cannot access more than about 8.4G
>of the drive, but is it safe to use DOS within that limit and share
>the drive with Linux?  I plan to move the drive to IDE2, the HPT
>controller, as soon as a new distribution is available with Linux 2.4.




 
 
 

1. problem with dos in partitioning a "large" EIDE disk.

Hello Linux wizards,

I have the following problem with the DOS partition on my hard-disk:
"fdisk" reports a size of 307 MB (both dos and linux "fdisk") for
the DOS partition, but "df" reports 343 MB. Also DOS Windows believes that it
has 343 MB. I learned this the hard way, because last time the dos partition
was almost full..., and it corrupted my linux root partition :-(

My disk is a EIDE Western Digital Caviar of 850 MB (from Jan. 1995), and has
thus more than 1024 cylinders (1654 cyl, 63 sec, 16 hd).  The one who installed
linux for me used the easiest trick to accommodate for disk: describe the real
disk geometry in the BIOS, and have all boot/root partitions in the first 1024
cylinders.

Why is the size reported by "fdisk" different than the one assumed by "df" and
windows?

"fdisk -l" reports the following for the DOS partition:

Device     Boot  Begin Start   End  Blocks    Id   System
/dev/hda1            1     1   610  307408+    6   DOS 16 bit >= 32M
                                    ^^^^^^^

What does the "+" mean after the number of blocks? I have the feeling that it
has to do with my problem...

I plan to resize my dos partition such that "df" reports some size smaller than
300 MB. So my linux installation will not be hurt anymore.  Is there a more
clever way to solve the problem?

Please (also) send your answers with e-mail.  I am not sure that I will be able
to check news in the first few days, and news is not stored very long over
here.

Thanks in advance,


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