An Xsan client or metadata controller (MDC) will experience a kernel panic if you do not unmount a volume from it before performing an action on that volume in Xsan Admin that will change the volume. Though you can change some settings for an existing volume, other changes require the volume to be re-initialized (you'll see a warning in these cases).
In order to avoid this behavior, unmount and stop Xsan Volumes before changing their configuration in any way that requires the volume to be rebuilt.