RFC: Project geom-events

[perryh at pluto.rain.com]

John <jwd at freebsd.org> wrote:
> > ... gpart should show warning message if user is trying to put
> > GPT on non real disk devices.
...
>    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.

The setting of $device is not shown, but I suppose it is the name
of the multipath provider.

I'm not familiar with gmultipath, but it would not surprise me if
(like most GEOMs) it were putting its metadata in the last block(s)
of its providers and therefore encountering the same issues as
gmirror and glabel.  In that case, the best fix may be to define
the multipathing per-partition instead of per-device (if that is
possible), or to use MBR/BSD instead of GPT for partitioning.