This disclosure uses both an administrative thread and multiple worker threads (N) to process the LUN on-lining work in parallel at both the volume level and the LUN level. When the administrative thread receives the message to start the initialization, the administrative thread assigns the work for reading the VTOC information for the LUNs in a volume to one or more worker threads and moves on to perform additional initialization tasks. N worker threads work on N volumes in parallel. These worker threads then independently send messages (e.g., asynchronous messages) to the file system layer, and once the file system layer is done loading the required buffers, the file system layer sends replies back to the administrative thread. The administrative thread then again assigns work to the worker threads to finally bring the LUNs on-line.