gmirror failed with error 19.

[Andrey V. Elsukov]

On 28.10.2011 13:48, Sascha Klauder wrote:
>  I've got bitten by this as well when trying a source up-
> grade of a freshly installed 8.2-RELEASE system that had
> gmirror configured after installation according to the 
> procedure in the Handbook.
> 
>  The 9.0-RC1 kernel drops to the mountroot prompt when
> booting with
> 
>  GEOM_MIRROR: Device mirror/gm0 launched (2/2).
>  GEOM_PART: partition 1 has end offset beyond last LBA: 490350671 > 490350670
>  GEOM_PART: integrity check failed (mirror/gm0, MBR)

This is the main problem. Your MBR' slice is bigger than actual space
you have. The only way to fix this - recreate slice.
You can break your mirror, recreate the slice (NOTE: you must preserve
one sector for the gmirror's meta-data), then copy your data to the
newly created slice, then reboot from the new slice and recreate mirror.

-- 
WBR, Andrey V. Elsukov