A data storage device is disclosed comprising a head actuated over a disk. The disk is spun at a first speed while writing first data to the disk based on a first disk format defining a first capacity for the disk. When a command is received from a host to spin the disk at a second speed different from the first speed, the disk is spun at the second speed while writing second data to the disk based on a second disk format defining a second capacity for the disk different from the first capacity.