More redundancy and MUX boards
Each controller has seven Gigabit ports with six used for data and the seventh dedicated to management duties. As both controllers are active, all twelve ports are available for data services with dual redundant links for management access as well.
Each controller has an external SAS port and the appliance supports up to 256 hard disks. You can daisy-chain Qsan's J300Q JBOD disk shelves over redundant links and these units also have dual PSUs and fans.
The appliance supports SAS drives but if you want to use SATA drives you'll need to fit Qsan's MUX interposer boards at the rear of each drive carrier. Costing around 40-50 each, these do negate the cost benefits of using cheaper SATA drives.
ZFS provides an impressive range of storage management features including deduplication
