gmirroring slices

[Hugo Silva]

Lorenzo Perone wrote:
>
> 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
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I setup an 8.0-RC3 server the other day just like this:

  Name    Status  Components
mirror/gm0s1  COMPLETE  ad4s1
                        ad6s1


 pool: storage
 state: ONLINE
 scrub: none requested
config:

    NAME        STATE     READ WRITE CKSUM
    storage     ONLINE       0     0     0
      mirror    ONLINE       0     0     0
        ad4s2   ONLINE       0     0     0
        ad6s2   ONLINE       0     0     0

errors: No known data errors


I would like to try setting this up with gpart too, but I had to get 
this server running asap and I knew I could make it work like this.