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

[Vivek Khera]

On Apr 6, 2006, at 4:12 AM, 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.

Well, my ovservation from using "diskinfo -t -v" on my /dev/ad4  
device and then on the /dev/mirror/gm0 device after the mirror create  
shows a slightly smaller mediasize.  Now, whether the UFS knows it is  
smaller or not, I can't say, but the lower level of the OS is  
reporting a smaller media size.

In any case, every time I partition a disk, fdisk always leaves a  
bunch of sectors hanging off the end. I presume that's where gmirror  
stores its data for whole-disk mirror... at least I'd hope!