Prioritized Spin-Up of Drives

A data storage system controller designates critical drives for staggered spin up and other, non-critical drives for spin up only when the controller notifies the appropriate expander. Each expander in the data storage system maintains configuration information for each PHY of the expander and reports completion of spin up when all of the drives designated "staggered spin up" have been spun up. Alternatively, an expander maintains PHY configuration data, designating each PHY as "staggered spin up," "host notify" or "disabled." At boot time, only devices connected to PHYs designated "staggered spin up" are spun up in cycles before reporting spin up completion to a host device.