On resizing a VxVM volume exported to a guest, the virtual disk still shows the old size of the volume. The virtual disk drivers do not update the size of the backend volume after the volume is resized.
Oracle has an RFE for this issue (CR 6699271 Dynamic virtual disk size management).
Workaround: The guest must be stopped and rebound for the new size to be reflected.
This Oracle (Sun) bug is fixed in Oracle (Sun) patch 139562-02.