gmirror on existing filesystem (was Fresh install on gmirror'ed disks?)

[Mike Jakubik]

Pawel Jakub Dawidek wrote:
> I can't give you an authoritative answer, because I don't know UFS
> internals so well. All I know is that it (UFS) thinks the last sector is
> available and may want to use it at some point getting EIO then.
> I'm not using this method, but I've heard of many people using it
> without problems.
>
>   

Thanks, I guess better safe than sorry then.

> Speaking about installer. I don't think I'll be able to add
> configuration of my GEOM classes to the sysinstall in the near future
> (and I hope never - I'd prefer to wait for a new installer).
>   

I wasn't suggesting you do it, i know there are people working on a new 
installer, and this has been mentioned already. It's on their "to do" 
list, but who knows when we will see it.

> One can still see how many sectors exactly has the partition he is going
> to create file system on and add additional newfs(8) flag
> '-s <sectors-1>'.
>   

"gmirror utility uses on-disk metadata (stored in the provider's last 
sector) to store all needed information."

Would creating a freebsd partition thats slightly smaller than the disk 
resolve the issue (when mirroring the entire disk)? or does it still use 
the last sector of the label? I'm not sure what one means by "provider" 
in this case.