The IBM PCI SSA 4-Port RAID Adapter serves as the interface between systems using the Peripheral Component Interconnect (PCI) architecture and devices using the Serial Storage Architecture (SSA). The adapters provide high-performance implementation of RAID-5 arrays. Each array can have from 2 through 15 member disk drives plus one for parity. Up to 32 arrays can be controlled by one PCI SSA 4-Port RAID Adapter or PCI.The adapters each provide 4 SSA ports for the attachment of storage devices such as hard disk drives. Each port operates at 20 MB/s full-duplex using point-to-point copper cables up to 25 meters long. As an alternative to copper cables, fiber optic cables can be used to link SSA nodes. Nodes linked by fiber optic cables can be up to 2.4 km (7874 ft) apart. Fibre-Optic Extenders, which are features of SSA units, connect the fiber optic cables to the SSA nodes. SSA retains the SCSI-2 commands, queuing model, status, and sense bytes; it is an industry-standard interface.