When using a compression ratio of 2:1 or 1:1 a second SCSI HBA (ATTO UL2D or UL3D) is required. 2:1 compression requires two drives connected across both channels of the Video HBA; 1:1 requires four drives across both channels. The drives can be striped using either ATTO ExpressRAID (version 2.3.2 or higher) or Avid Drive Utility 2.1 or higher. Simply select the drives and format them as a striped set. Note: 3:1 compression with AV OptionXL does not require a second SCSI HBA or striped drives.