Extended partition creation policy ?

["David Balazic" <david.balazic@hermes.si>]

Hi!

(please CC me on replies, as I am not subscribed to the list; but will
check its archives every now and then)

I noticed, that when the debian installer is instructed to create
two partitions, whose joint size is less than the size of the disk,
then it creates one primary partition and one logical partition inside
an extended partition.

The issue is, that this extended partition has the size of the logical
partition and not the maximum possible size (the entire empty disk space
plus the logical parition).

This layout seems to be special to debian, since all other distros
(except debian based ones) and operating systems create extended
partitions that cover the entire free disk space.

This becomes a problem, when the user want to create a new partition.
He has two options :
 - create a primary partition
   up side : easy to do, no problems
   down side : as two slots are used for the original primary partition
   and the extended partition, only two remain. Also more than than one
primary
   partition is unrecomended and can be problemtatic in certain
environments.

 - change the size of the extended partition and create logical
partition(s)
   upside : no limits on number of partitions, no other problems
   downside : very few partitioning tools support this in asimple and
obvious way.
   The most common ones (fdisk, Windows Disk Management) for example do
not.


My question is : What benefit does the debian way give ? Is there a
possibility
to change for the other "common" way ?

For reference I also include the results of a small research about this
on
various op-systems :

I started their CD based installer and in their
partitioner, I created two partitions (a single partition
setup usually creates a primary partition, so that would
not cover our topic).
I always used the default settings and values, except the following :
 - I asked creation of exactly two partitions
 - I specified their size (the sum of their sizes is less than the disk
size)
 - for linux, I specified the partition type for the second partition as
"swap" 
   (the first partition was formatted by the default FS and used for / -
root fs)

That's it. The results :

win XP             : extended partition covers entire disk
win 98             : extended partition covers entire disk
debian 2.0 hamm    : extended partition covers only used part of disk
redhat 5.2         : extended partition covers entire disk
debian 3.1 sarge   : extended partition covers only used part of disk
fedora 4           : extended partition covers entire disk
   (FC4 : I created 4 partitions, otherwise no extended partition would
be created,
         but 3 primary partitions)

As we see, the "small extended partition" is a debianism.

Notes :
"entire disk" means "entire disk minus the part used by the primary
partition"
"only used part of disk" means "the space used by the logical partition"

Regards,
David

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http://noepatents.eu.org/          Innovation, not litigation !
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David Balazic                      mailto:david.balazic@hermes.si
HERMES Softlab                     http://www.hermes-softlab.com
Zagrebska cesta 104                Phone: +386 2 450 8846 
SI-2000 Maribor
Slovenija
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