 The host computer communicates with the disks in the enclosure via a SCSI interface which may be Parallel SCSI, FC-AL, SAS, or SSA.One of the disk devices located in the enclosure is set up to allow SCSI Enclosure Services (SES) communication through a logical unit.The disk-drive then communicates with the SES processor in the enclosure, usually via Enclosure Services Interface (ESI), or a protocol called DSI for SSA enclosures.