Subject: Re: wedges and what does that mean?
To: Johnny Billquist <email@example.com>
From: Bill Studenmund <firstname.lastname@example.org>
Date: 09/05/2006 11:15:04
Content-Type: text/plain; charset=us-ascii
On Mon, Sep 04, 2006 at 01:58:31PM +0200, Johnny Billquist wrote:
> So, what are you saying?
> Are wedges just partitions with another name, or is there really a=20
> The actual width of the size and offset is hardly a reason to say it's=20
> different. Is the information about wedges not stored on the disk? How=20
> do you find them in that case?
> I'm probably dense, but this answer made it look no different from a=20
> partition, except the fact that they were 64-bit values. Which is nice,=
> but it don't really make them any different.
Most of the differences are conceptual.
The thing about our partitions is that they really really are entries in a=
struct disklabel. And struct disklabel is an on-disk format. So there's no=
way to change "partition"s without changing the on-disk format.
Thus a conceptual change to get us out of the difficulty.
wedges are partitions separated from the partitioning scheme that defined=
them. So you don't need a struct disklabel, or struct part_map_entry, or=20
any other struct.
Since there's a disconnect between the on-disk representation and the=20
in-kernel one, you can map anything into a wedge.
Another part of the conceptual plan is that we move partition reading out=
of the kernel into userland. The kernel only NEEDS to be able to find the=
root partition, then userland can find all the rest. As a convenience, you=
can (according to the plan) add support for different partitioning schemes=
in the kernel.
We aren't there yet, and things don't work according to the plan. But=20
we're getting there. :-)
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