Re: [patch] NetBSD disklabel support for geom_bsd

Dmitry Pryanishnikov <dmitry_at_atlantis.dp.ua> wrote:

>   Look at my HDD layout from the POV of FreeBSD and NetBSD (I'll show
> some 
> parts sufficient to understand the idea), start and size are in disk
> sector 
> units:
> 
>      HDD area              FreeBSD  NetBSD  Description in the
>    Start       Size        device   device     FreeBSD terms
> 
>          0  312579695      ad0      wd0d    Whole HDD
>         63    2088387      ad0s1    wd0e    First slice (DOS)
> 147942585   81931500      ad0s3    wd0c    Third slice (NetBSD)
> 147942585    2097648      ad0s3a   wd0a    Partition 'a' of the 3rd
> slice
> 150040233    2097648      ad0s3b   wd0b    Partition 'b' of the 3rd
> slice
> 
> Of course, you'll get ad0s3a,b only after applying my patch, otherwise
> they
> aren't accessible from the FreeBSD.
> 
>    I hope you'll see what they do:
> 
> 1. NetBSD's 'c' partition describes NetBSD slice (always?).
> 2. NetBSD's 'd' partition describes the whole HDD (always?).

AFAIK, statement (2) above holds only for a few architectures.
According to the NetBSD disklabel man page, the "d" partition refers to
the whole disk only on i386, hpcmips and arc platforms.  On the rest,
the whole disk is referred to by the "c" partition.

I run NetBSD/alpha, and I've always used the "c" partition to refer to
the whole "raw" disk.  (I usually use the "d" partition for /var
or /usr.)  Furthermore, on NetBSD/alpha there's no concept of "slices,"
so far as I'm aware.

Here is the partition table for drive sd0 on my NetBSD/alpha system:

8 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:    262144         0       RAID                     # (Cyl.      0 -    115*)
 b:    524288    262144       RAID                     # (Cyl.    115*-    347*)
 c:   8380080         0     unused      0     0        # (Cyl.      0 -   3707)
 d:   3483168    786432       RAID                     # (Cyl.    347*-   1889*)
 e:   4110480   4269600       RAID                     # (Cyl.   1889*-   3707)

(Most of my system is mirrored via RAIDframe.)

I don't know if FreeBSD/alpha has the notion of slices, as it's not
supported on my Turbochannel alpha and so I've never run it...

Cheers,

Paul.
-- 
e-mail: paul_at_gromit.dlib.vt.edu

"Without music to decorate it, time is just a bunch of boring production
 deadlines or dates by which bills must be paid."
        --- Frank Vincent Zappa