Subject: Re: wedges and what does that mean?
To: None <>
From: Martin Husemann <>
List: current-users
Date: 09/04/2006 13:34:39
On Mon, Sep 04, 2006 at 01:02:16PM +0200, Bernd Ernesti wrote:
> could someone please give me and others an overview what does it mean

Let me try.

Wedges are parts of a disk. They do not have partitions - for example
on this machine I'm typing this on I have /dev/dk0 and /dev/dk1 -
but there is no /dev/dk0a.

They can be created by userland, via dkctl, or some other tools (for example
mbrlabel could/should be enahnced to optionally created wedges from the
parsed label).

They also can be created by the kernel, for example to allow booting
from a wedge. This is called autoconfiguration, and it is controlled
via options DKWEDGE_METHOD_....

But wedges have no inherent corelation to some on-disk partition format,
like the disklabel which the old partition code used. Lots of magic/evil
code will disapear from the kernel once the wedge conversion is complete.

> I heard that it would be possible to use more then 2TB and that the old
> disklabel way will go away.

Yes. Wedges have 64 bit offset and size (both in blocks). One supported
method to store information on disk is the EFI/GPT (Guid Partition Table)
format, where you can store this big values (and have upto ~64k partitions
per disk)

> What does this mean to a machine which currently uses disklabel and how
> are wedges configured?

A machine can easily be converted by enabling the proper DKWEDGE_METHOD_*
options to have the kernel autoconfigure the wedges needed for booting.
Besides that, you need a few obvious changes to /etc/fstab - and that's
it. No > 2TB partitions when using the old on-disk formats though.