SCSI back-end layer

The small computer system interface (SCSI) back-end layer on the system supports external storage systems.

The SCSI back-end layer performs the following functions:

Controls access to individual external storage systems that are managed by the clustered system.
Receives requests from the virtualization layer, processes them, and then sends them to managed disks (MDisks).
Addresses SCSI-3 commands to the storage systems on the storage area network (SAN).

External storage systems and logical units

External storage systems reside on the SAN fabric and are addressable by one or more worldwide port names (WWPNs). An external storage system might contain one or more logical units (LUs), each identified by a different logical unit number (LUN). External storage systems that are managed by the system typically contain multiple LUs.