RFC: Project geom-events

[John]

----- Miroslav Lachman's Original Message -----
> Lev Serebryakov wrote:
> >Hello, Miroslav.
> >You wrote 6 ?????????????? 2011 ??., 16:59:19:
> 
> [...]
> 
> >>The current state is simply wrong, because user can do something what
> >>cannot work and is not documented anywhere.
> >   It is Ok in UNIX way, in general. You should be able to shoot your
> >  leg, it is good :)
> 
> I am sorry for my late reply.
> Foot shooting is OK, if somebody wants to shoot his foot, but I don't 
> want to shoot my foot if I am aiming at my head :)
> 
> >   But if geom_label doesn't reduce its provider to count its own
> >  metadata, it looks like a bug!
> 
> As Ivan Voras explained, it is not a bug, it is just a matter of mixing 
> two things thant can't coexist together. So the problem is that it is 
> not mentioned anywhere in the FreeBSD docs. (Thank you Ivan for your 
> explanation!)
> And as somebody else already mentioned in this thread, it should be 
> documented in manpages and Handbook and gpart should show warning 
> message if user is trying to put GPT on non real disk devices.
> 
> As is mentioned in the thread "Memstick image differences between 8.x 
> and 9.x", the GPT brings more problems by requirement of second table at 
> the end of the device (so disk image cannot be easily written by dd on 
> bigger disk)

   This also seem to prevent something useful like:

# camcontrol inquiry da0
pass2: <HP EH0146FAWJB HPDD> Fixed Direct Access SCSI-5 device 
pass2: Serial Number 3TB1BKGX00009036W9EN
pass2: 600.000MB/s transfers, Command Queueing Enabled
# camcontrol inquiry da25
pass27: <HP EH0146FAWJB HPDD> Fixed Direct Access SCSI-5 device 
pass27: Serial Number 3TB1BKGX00009036W9EN
pass27: 600.000MB/s transfers, Command Queueing Enabled

# gmultipath label ZFS0 da0 da25
# gpart  create -s gpt $device
# gpart  add    -s 128    -t freebsd-boot                $device     # Create 64K boot partition
# gpart  add    -s 4m     -t freebsd-ufs  -l mb$dev      $device     # small partition
# gpart  add              -t freebsd-zfs  -l $dev        $device     # Remaining space for zfs

   It seems like protecting your partitions with multiple
paths would be a good thing.  I've been experimenting with this
and end up with corrupt partitions.

   Am I missing something?

-john