DragonFly BSD
DragonFly kernel List (threaded) for 2004-03
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Re: Disk partitioning (was: Daemon's Advocate article)

From: Joerg Sonnenberger <joerg@xxxxxxxxxxxxxxxxx>
Date: Wed, 3 Mar 2004 13:26:39 +0100

On Wed, Mar 03, 2004 at 11:23:42AM +1030, Greg 'groggy' Lehey wrote:
> The restrictions on the different types of partitions come from
> different places:
> - BIOS ("primary") partitions are limited by the BIOS, in particular
>   the MBR.

This is the 4 primary partition at one time limit. There are some boot
loaders which can change the MBR before booting an OS and can partly
circumvent that limit.

> - Extended Microsoft partitions are limited by Microsoft's software.
>   That will be what limits them to a single extended partition.  Linux
>   also (ab)uses this partition type.  It's conceivable that it
>   understands more than one extended partition.

The worst thing about extended partitions is there chaining, which could
be used to kill quite a lot of OSes at boot when specifying the MBR as
location of the extended partition.

> - BSD slices look very similar to Microsoft extended partitions.  At
>   least under FreeBSD, you can up to four partitions, one per slice.
>   There may be problems with NetBSD and OpenBSD in this environment,
>   due to the partition naming conventions.  I don't expect Dragonfly
>   to have any problems.

NetBSD and OpenBSD have the advantage of allowing the specification of
subartitions outside the slice and therefore the use to access e.g. such
hidden partitions from point 1. FreeBSD has a limit of 8 partitions,
OpenBSD and maybe NetBSD too of 16.


> Greg
> --
> Note: I discard all HTML mail unseen.
> Finger grog@xxxxxxxxx for PGP public key.
> See complete headers for address and phone numbers.

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