gconcat file system damage

[Andrew Snow]

How did you expand the filesystem onto the new volume?  UFS2 expansion 
is not supported.

> I originally created the concatted disk in two steps. First I created 
> the concat on my new mirrored disks and copied the files from my 
> existing mirror in there. Second I appended the existing mirror to my 
> concatted disk. It seemed to work fine, but now I'm seeing so much 
> errors that I can only mount the concat r/o!