gmirroring slices

[Lorenzo Perone]

Hello,

I was wondering if anyone could give me an advice on how viable and  
reliable it is, to use gmirror on a slice of an MBR-style partitioned  
disk, and use the second slice(s) within a zpool.

I remember a discussion here on where metadata is kept (always at the  
end of the disk as opposed to the end of the given consumer?), so I  
wasn't sure about how much of a good idea this might be. The reason  
I'd like to have it like this is, that I had mixed bad experiences in  
the effort of using ZFS as a boot and root volume, so I'd rather keep  
a traditional slice for booting/rooting, and a zpool for the  
production jails on that machine.

The example would be

provider: mirror/gm0
consumers: ad6s1 and ad8s1

zpool mirror made out of
ad6s2 and ad8s2

while experimenting, I got into the problem that gmirror label -v -b  
round-robin gm0 ad6s1 got a permission denied (even with sysctl  
kern.geom.debugflags=16/17). Any hints on what can cause this (I might  
have screwed up something with fdisk/bsdlabel, but after  
doublechecking I wonder what it could be..)

Is a GPT partition table better for this (I got further with another  
machine by using GPT partitions)?

Thanx for any advice.

Regards,
Lorenzo