Sans Digital TowerRAID 4-Bay RAID Tower Performance Bundle TR4M-BHA (Black) Bundled with RR2314 RAID controller card for over 200MB/s RAID 5 performance. 4 eSATA ports PCIe x4 RAID controller supports up to 4 units or 16 hard drives in a single or multiple RAID array. 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.