partitioning dilemma

[Aragon Gouveia]

Hi,

Between MBR and GPT, I'm struggling to find the right partitioning 
scheme to meet my requirements.  Suggestions on below would be highly 
appreciated.

I have 2 disks.  I want 2 independent gmirror volumes, ie. 2 partitions 
on each disk, with one partition from each disk in a gmirror volume. 
Each gmirror volume would contain a bootable FreeBSD system (BSD label), 
and I'd selectively boot between them when testing new releases or other 
big changes.

Then I'd like a 3rd partition on each disk, both of which for swap space.

Then a 4th partition on each disk which I plan to use as a ZFS mirrored ZIL.

Finally, a 5th partition on each disk which would both serve as ZFS L2ARC.

My dilemma:

All documentation and mailing list discussion about GPT seems to 
indicate that creating BSD labels inside GPT partitions is a Bad Idea, 
which would mean putting two GPT partitions into a gmirror volume is a 
bad idea.  Is this still the case?

My attempts at using MBR and EBR instead of GPT are discouraging once I 
get to the point of creating an EBR.  From what I can gather, default 
kernel build options specify "options GEOM_PART_EBR_COMPAT" which 
prevents GEOM from editing EBR partition schemes:

# gpart show ada3s4
=>        0  267068592  ada3s4  EBR  (127G)
           0  267068592          - free -  (127G)

# gpart add -s 67221504 -t freebsd ada3s4
gpart: pre-check failed: Operation canceled

Ok, so I guess I can recompile without that kernel option, but I'm sure 
there's a good reason it's a default option... Is EBR also considered a 
Bad Idea?

Any suggestions?


Thanks,
Aragon