Capacity expansion on a Pure Storage FlashArray is a highly controlled, safe process. When an Implementation Engineer physically unboxes and inserts a new data pack (a group of DirectFlash Modules) into the available drive bays of a chassis or a DirectFlash Shelf, the Purity operating system detects the hardware instantly. However, it does not automatically wipe the drives and assimilate them into the global storage pool.

Instead, the newly inserted modules are placed into a safe, quarantined state known as 'unadmitted.' This intentional design choice prevents catastrophic data loss in the event that an engineer accidentally inserts a drive containing live data from another system, or inserts drives before the customer is financially or operationally ready to activate the new capacity.

To officially claim the drives, integrate them into the system's Wide Write Groups (WWGs), and initiate the background parity redistribution process, the Implementation Engineer must explicitly authorize their use. This is accomplished by running the puredrive admit command. The engineer can either specify the exact drives (e.g., puredrive admit CH0.BAY10 CH0.BAY11...) or use a global flag like puredrive admit --all if all unadmitted drives are ready for ingestion. Once admitted, the drives transition to a 'healthy' state, and the array's total usable capacity increases seamlessly without any host disruption.