Zero Downtime Hard Disk Firmware Update

An embodiment includes determining which disks need an update, then copying user data from a disk to be updated to a spare disk. New data is written to both the disk to be updated and the spare disk, and a zone map is maintained for all volumes of the disk to be updated. The firmware on the disk is updated, and changed data is copied from the spare disk to the newly updated disk based on the zone map. New data is written to both the newly updated disk and the spare disk. Once the changed data has been copied to the newly updated disk, data is written to the newly updated disk.