Specifications
are used to interconnect the fibre-channel ports. For information about the ESS
three basic topologies you can use with the ESS, see “Fibre-channel architecture”.
Fibre-channel architecture
The ESS provides a fibre-channel connection when your IBM SSR installs a
fibre-channel adapter card (shortwave or longwave) in the ESS. For more
information about hosts and operating systems that the ESS supports on the
fibre-channel adapters, see the ESS Web site:
www.storage.ibm.com/hardsoft/products/ess/supserver.htm
Fibre-channel architecture provides a variety of communication protocols on the
ESS. The units that are interconnected are referred to as nodes. Each node has
one or more ports.
An ESS is a node in a fibre-channel network. Each port on an ESS 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.
ESS architecture supports three basic interconnection topologies:
v Point-to-point
v Switched fabric
v Arbitrated loop
Point-to-point topology
The point-to-point topology, also known as direct connect, enables you to
interconnect ports directly. Figure 5 shows an illustration of a point-to-point topology.
The ESS supports direct point-to-point topology at a maximum distance of 500 m
(1500 ft) with the shortwave adapter. The ESS supports direct point-to-point
topology at a maximum distance of 10 km (6.2 mi) with the longwave adapter.
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 ESS supports up to 100 km (62 mi) with a
storage area network (SAN) or other fabric components.
S008944L
1
2
Legend
1 is the host system.
2 is the ESS.
Figure 5. Point-to-point topology
Chapter 1. Introduction 13