A servo circuit includes a servo channel and a processor. The servo channel recovers servo data from servo wedges that identify respective data sectors on a data-storage disk. On spin up of the disk, the processor detects a spin-up wedge associated with one of the servo wedges and then detects the servo wedge. Once the servo wedge is detected, a head-position circuit can read the location data from the servo wedge to determine an initial position of the read-write head. By detecting a both a spin-up wedge and a servo wedge to determine an initial head position on disk spin up, such a servo circuit often allows one to increase the disk's storage capacity by reducing the lengths of the spin-up wedges.