Dear forum members: I am monumentally sorry to bug you, but I do need your help badly indeed! To the best of my ability, let me describe the situation for you. Setup TowerRAID DASD (http://www.sansdigital.com/towerraid/tr5utb.html) is equipped with 5 Western Digital 2 TB 7200 RPM HDDs operating in JBOD mode. TowerRAID is directly connected via USB2.0 to Mac mini working under Mac OS X 10.8.6. All HDDs in my system are Mac OS Extended (Journaled) formatted. Problem While using TowerRAID to Read/Write large amounts of data (0.3TB - 1TB usually), connection is almost always (in 90% of the cases, I would say) lost during the process. Connection is always lost if TowerRAID, while idling, is left connected to Mac mini for more than 5 - 6 minutes. Error message I always get: The disk was not ejected properly. If possible, always eject a disk before unplugging it or turning it off. To eject a disk, select it in the Finder and choose File > Eject. The next time you connect the disk, Mac OS X will attempt to repair any damage to the information on the disk. Note External USB HDDs always working (during Read/Write/Idling) without any problems in my setup: Western Digital My Book Essential and Seagate FreeAgent. Please, please help me at your earliest opportunity!