Fibre-channel architecture provides a variety of communication protocols on the storage unit. The units that are interconnected are referred to as nodes. Each node has one or more ports.
A storage unit is a node in a fibre-channel network. Each port on a storage unit fibre-channel host adapter is a fibre-channel port. A host is also a node in a fibre-channel network. Each port attaches to a serial-transmission medium that provides duplex communication with the node at the other end of the medium.
- Point-to-point
- Switched fabric
Point-to-point topology
The point-to-point topology, also known as direct connect, enables you to interconnect ports directly. Figure 1 shows an illustration of a point-to-point topology.
- 1 Gb shortwave adapters have a maximum distance of 500 meters (1640 ft)
- 2 Gb shortwave adapters have a maximum distance of 300 meters (900 ft)
- 2 Gb longwave adapters have a maximum distance of 10 kilometers (6.2 mi)
Switched-fabric topology
The switched-fabric topology provides the underlying structure that enables you to interconnect multiple nodes. You can use a fabric that provides the necessary switching functions to support communication between multiple nodes.
You can extend the distance that the storage unit supports up to 300 km (186.3 miles) with a storage area network (SAN) or other fabric components.
The storage unit supports increased connectivity with the use of fibre-channel (SCSI-FCP and FICON™) directors. Specific details on status, availability, and configuration options that are supported by the storage unit are available on http://www-1.ibm.com/servers/storage/disk/ds6000.
The storage unit supports the switched-fabric topology with point-to-point protocol. You should configure the storage unit fibre-channel adapter to operate in point-to-point mode when you connect it to a fabric topology. Figure 2 shows an illustration of switched-fabric topology.
Arbitrated loop topology
Fibre Channel Arbitrated Loop (FC-AL) is a ring topology that enables you to interconnect a set of nodes. The maximum number of ports that you can have on an FC-AL is 127. Figure 3 shows an illustration of an arbitrated loop topology.
The storage unit supports FC-AL as a private loop. It does not support the fabric-switching functions in FC-AL.
The storage unit supports up to 127 hosts or devices on a loop. However, the loop goes through a loop initialization process (LIP) whenever you add or remove a host or device from the loop. LIP disrupts any I/O operations currently in progress. For this reason, you should only have a single host and a single storage unit on any loop.
