8.0-RELEASE and "dangerously dedicated" disks

[George Davidovich]

On Tue, Dec 01, 2009 at 08:34:05PM -0800, Randi Harper wrote:
> I'm going to just reply to all of these at once.
>
> On Tue, Dec 1, 2009 at 1:03 PM, Jerry McAllister wrote:
> > On Tue, Dec 01, 2009 at 07:59:42AM -0500, Maxim Khitrov wrote:
> > > On Sat, Nov 28, 2009 at 12:28 PM, Peggy Wilkins wrote:
> > > > Due to history I won't go into, all my production (currently
> > > > 7.2-RELEASE) systems are installed onto "dangerously dedicated"
> > > > disks.  What exactly do I need to do to upgrade them to 8.0?
> > > > (I'm not asking for an upgrade procedure, I'm familiar with
> > > > that, but rather, how this change impacts the upgrade.) I think
> > > > that the suggestion that the disks need to be reformatted is
> > > > extreme and I hope something less extreme will suffice.
>
> Just to point out the obvious, you shouldn't use "dangerous" and
> "production" in the same sentence. :)

Fun with ambiguities aside, I think it's fair and reasonable to
interpret "dedicated" as "dedicated to FreeBSD", and "dangerous" as "may
not work with common third-party disk tools or an older BIOS".  

It's similarly fair to interpret any caveat, implicit or otherwise,
against using "dangerously dedicated mode" as a general recommendation
aimed at new users (typically in dual or multi-boot environments), and
not a statement that dangerously dedicated mode is unsuitable for
production environments.  It certainly doesn't state or suggest that
it's a convenient but deprecated feature that might be removed without
notice or warning in the future.  Which is what's happened.

In that light, the statement in the release notes merits a fuller
description as well as an explanation for the change. 

> > > > Also, just to be clear, does this statement refer to boot disks,
> > > > data disks, or both?
> > > >
> > > > 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?
> >
> > I don't know why it would have an affect, but they say it does.
>
> Did you see all the mailing list chatter about new installations                          
> failing due to sysinstall not being able to newfs device names that                       
> didn't exist? This is related. Also, a partition table isn't just a                       
> partition table. It's a little more complex than that. It has                             
> *nothing* to do with the filesystems inside. It has everything to do                      
> with the way that FreeBSD looks at the drive to figure out what's on                      
> it. See man pages for geom/gpart. There are others that have given a                      
> better explanation than I can provide (marcus, juli). Search the                          
> archives. 

FreeBSD is known for, among other things, the consistent quality of its
documentation.  As it stands, the statement "dangerously dedicated mode
for the UFS file system is no longer supported" in the release notes
stands in direct contradiction to the official Handbook (updated to
include 8.0-RELEASE) Section 18.3.2.2 which states "you may use the
dedicated mode".

A suggestion to search the (multiple) archives for chatter suggests that
authoritative information can now be found on display in the bottom of a
locked filing cabinet stuck in a disused lavatory with a sign on the
door saying "Beware of the Leopard".

Perhaps you could provide something more specific, or a direct link to
the chatter? 

> Trust me, I didn't remove DD support from sysinstall just to                    
> make life more complicated for everyone. I did this because as it                         
> stands right now, it doesn't work. 

Regrettably, the end result is the same.  That's not to say we wouldn't
grumble and then happily settle for something less.  Provided that
something amounted to more than "no longer supported because it doesn't
work".

-- 
George