On Mon, Feb 08, 1999 at 12:43:14PM -0500, Andrew Brown wrote:
> On Sun, Feb 07, 1999 at 12:47:05AM -0600, Brian C. Grayson wrote:
> >  One thing I've never heard discussed in the partition-wars is,
> >why do we not support extended partitions?  From what I've heard,
> >one can have an unlimited number of partitions in an extended
> >partition, or at least a whole bunch (>16?) of them.
> 
> typically, you get space in the main partition table (in sector zero)
> for four "primary" partitions.  all the fdisk implementations i've
> seen will let you make *one* of those into an extended partion, with
> it's own four partitions.  and that's been the limit i've seen so far.

  I heard that you could have more than 4 partitions in an
extended partition.  It appears that each extended partition can
hold one partition, and a chain to another extended partition.

http://www.firmware.com/support/bios/fdisk.htm:

"MS-DOS 3.3 -Maximum partition size - 32MB
	     First DOS version to allow extended DOS partitions.
 	     Maximum number of partitions - 24 (C: through Z:)"

http://www.users.intercom.com/~ranish/part/help.htm:
  "To have more than four partitions DOS uses Extended DOS
  partition scheme. This scheme allows you to have as much as 23
  DOS volumes on one physical drive."

http://www.ridgecrest.ca.us/~markee/Landis/howpt.htm:
  "2) In an extended partition there can be 0-1 "secondary"
     partition entries and 0-1 extended partition entries.

     What do I mean when I say the partition records (tables) form
     a "linked" list?  This means that the MBR has an entry that
     describes (points to) the first extended partition, the first
     extended partition table has an entry that describes (points
     to) the second extended partition table, and so on.  There is,
     in theory, no limited to out long this linked list is.  When
     you ask FDISK to show the DOS "logical drives" it scans the
     linked list looking for all of the DOS FAT type partitions that
     may exist.  Remember that in an extended partition table, only
     two entries of the four can be used (rule 2 above)."


  I like that "in theory" quote above.  DOS et al are limited to
24, since they use letters of the alphabet, but it appears that
a Real Operating System really could keep chaining.  At 6
usable BSD partitions each, one could theoretically easily have
over 200 partitions per disk.

  Brian