The space reclamation process runs in the background. You can monitor the Space Reclaimer progress in the status bar at the bottom of MMC.
Note: SnapDrive might indicate that it is necessary to run Space Reclaimer again after it has successfully completed a space reclamation process. This can happen if data is deleted from a LUN while Space Reclaimer is running. It is strongly recommended that no read/writes are performed during the space reclamation process.