The TowerRAID TR4M-BP is a compact RAID tower utilizing the latest SATA II port multiplier feature, where one single eSATA cable connects to four 3Gpps SATA II hard drives. Bundled with a high performance RAID controller card RR622, its RAID 5 performance is capable of reaching over 200MB/s. Online expansion is a feature included in the controller card so that RAID could be expanded without the need to recreate the storage space or erase the existing data. Advanced monitoring functions include real time hard drives health status and e-mail notification for critical events. Designed with easy installation in mind, the trayless TR4M-BP allows instant setup by simply inserting the hard drives after opening the protective ventilating cover. The included dual-port eSATA 6Gb/s PCIe 2.0 x1 RAID controller card allows the connection of up to two TR4M-BP units (up to 8 hard drives) using only two cables, while all drives could be configured into a single or multiple RAID arrays, providing over 200MB/s in performance. Bundled with RR622 RAID controller card for over 200MB/s RAID 5 performance. Dual-port eSATA 6Gb/s PCIe 2.0 x1 RAID controller supports up to 2 units or 8 hard drives in a single or multiple RAID array. Backward compatible with PCIe 1.0. Supports RAID 0, 1, 10, 5, 5+ spare, spanning and JBOD. Supports online expansion to expand capacity without the need to recreate the RAID volume and erase the existing data. Built-in real time hard drive health monitoring and e-mail notification for critical events. Supports PC, Linux and MAC OS, including Windows 7 and Snow Leopard. Accesses four hard drives using only one cable. Host interface: eSATA with Port Multiplier. Drive interface: 4 x 3.5" SATA I / SATA II.