The MSA 20 cabinet supports up to twelve 1" SATA 1.5Gb/s hard drives, for a maximum of 3TB of storage capacity using HP 250GB SATA 1.5Gb/s 1" hard drives. MSA 20 is designed for a high level of data protection. It includes redundant fans and power supplies (standard), battery-backed cache, and RAID ADG (standard). The MSA 20 feature familiar configuration and management tools such as Smart Array Configuration Utility and Insight Manager. Online Management Features: Online Capacity Expansion, Online RAID Level Migration, Online Stripe Size Migration, Online Spares (Global), User Selectable Read/Write cache, User Selectable Expand and Rebuild Priority. The MSA 20 is designed and qualified for ProLiant servers. This is the highest level of RAID fault tolerance. It allocates two sets of parity data across drives and allows simultaneous write operations. This level of fault tolerance can withstand two simultaneous drive failures without downtime or data loss.