The pass number, a number in the range 0–9, determines the order in which a particular mirror is resynchronized during a system reboot. The default pass number is 1. Smaller pass numbers are resynchronized first. If 0 is used, the mirror resynchronization is skipped. A pass number of 0 should be used only for mirrors that are mounted as read-only. Mirrors with the same pass number are resynchronized at the same time.