This bar shows whether you can create a node and wake a stopped node with its files intact. A real node tests this every hour, through the same API calls that customers make. The check creates the smallest node, writes a marker file, stops the node, and moves its disk to durable storage. Then it wakes the node, restores its disk, and reads the marker back. A second hourly check saves an object to the in-region storage that holds snapshots of GPU nodes, and reads it back. Green means that a stopped node woke with its files intact. A sold-out fleet stays green, because a full queue is healthy.