fibre channel switch (SAN)
The FC switch is the central component of Fibre Channel-based storage area networks( SAN). Depending on the FC topology and the requirements for availability, scalability and performance, a distinction is made between directors and switching fabrics in FC switches.
The topology is star-shaped with a logical ring structure. The FC switch forms the star point. Theoretically, such an FC switch could switch and manage 16 million FC ports or devices. In this FC topology, bandwidth is not shared; each connection between two switch ports has an allocated bandwidth.
The FC bus is comparable to a SCSI bus. Various protocols can be run on the FC bus; SCSI-3 is intended for streaming processes, but TCP/ IP, Internet Small ComputerSystem Interface over IP( iSCSI), Internet Fibre Channel Protocol( iFCP), High Performance Parallel Interface( HIPPI) or Fibre Channel Arbitrated Loop( FC-AL) can also be used. Of the five connection methods, called Class, Class 3 plays the dominant role because of its use of the SCSI 3 protocol. Class 3 is used to establish a connectionless service that operates without acknowledgement. The data transfer is nevertheless very reliable because data is only exchanged between the devices when a secure connection has been established. If FC-AL is used, the switch only has a limited addressing option, which refers to a maximum of 126 devices due to the 8-bit addressing in the FC-AL protocol. This restriction applies in the same way when FC hubs are used.
The distance between two devices connected to the FC bus can be up to 10 km (50 miles). If several devices are active on the bus, the bus length is reduced to approx. 1,200 m. The signal of the FC bus is regenerated by each device, unlike SCSI. The transfer rate is 100 MB/s, which must be shared by all devices in FC-AL; however, due to the switching technology, the maximum transfer rate is available to each device.