8.0-RELEASE and "dangerously dedicated" disks

[Jerry McAllister]

On Wed, Dec 02, 2009 at 10:30:10AM -0500, Bob Johnson wrote:

> On 11/28/09, Peggy Wilkins <enlil65 at gmail.com> wrote:
> > Can someone elaborate on what exactly this statement in the 8.0
> > detailed release notes means?
> >
> > http://www.freebsd.org/releases/8.0R/relnotes-detailed.html#FS
> >
> >> 2.2.5 File Systems
> >>
> >> ?dangerously dedicated? mode for the UFS file system is no longer
> >> supported.
> >>
> >>  Important: Such disks will need to be reformatted to work with this
> >> release.
> >
> [...snip...]
> >
> > It doesn't make sense to me that "dangerously dedicated" could have an
> > impact on UFS filesystems specifically.  A partition table is just a
> > partition table, regardless of what filesystems might be written on
> > disks, yes?  Am I misunderstanding something here?
> >
> 
> Unless someone has changed the meaning of the term in the last few
> years, a "dangerously dedicated" disk is one that has the FreeBSD file
> system on it with no partition table. It is basically an artifact of
> the pre-Microsoft origin of BSD (there were reasons it stayed around,
> but they ought to be ancient history by now). Since UFS is the
> standard FreeBSD filesystem, DD disks contain UFS filesystems almost
> by definition.
> 
> So, to get to the main point of your confusion (and unless I am the
> one that is very confused), "dangerously dedicated" disks do not have
> partition tables. That's what makes them dangerous. It confuses things
> that expect to find a partition table.
> 
> If your partition name has an "s" (slice number) in it (e.g. ad2s1a)
> it is not "dangerously dedicated". A "DD" disk partition would have a
> name like "ad2a" with no slice number. At least, that's the way it
> used to be. I quit using DD disks years ago when it became clear to me
> that the unintended side effects aren't worth the few bytes you save.
> Every once in a while a BIOS, or a utility, or something else pops up
> that expects to find a partition table and gets confused without it.
> It appears that it has happened again.
> 
> > Thanks for helping to clear up my confusion...
> 
> I hope I helped.

Good.   Except that in FreeBSD land you are talking about a slice table.
To carry things forward consistently, the partition table is within
a slice and describes FreeBSD partitions a..h (and more now I guess).
Only in MS or Lunix land should primary divisions be called partitions
and then they are _primary_ partitions.

But, even some of the fdisk and other documentation still mucks this
up and occasionally refers to slices as partitions.   Maybe we can
come up with some new terminology like  'blobs'  and  'dollops'  to get 
away from the problem.

////jerry    
   
> 
> -- 
> -- Bob Johnson
>    fbsdlists at gmail.com
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