5.6 Fibre Channel Arbitrated Loop Hub

Figure 5-8. A3724A/A4839A FC-AL Hub


The FC-AL hub is available in shortwave and long-wave models. Both models are available in stand-alone or factory-racked configurations. The AZ models are the factory-racked models.

5.6.1 Features

  • The shortwave hub has ten non-OFC shortwave optical transceivers.

  • The long-wave hub has nine non-OFC, shortwave optical transceivers and one non-OFC, long-wave optical transceiver.

  • Local retime and regeneration of transmit signals to prevent accumulation of jitter and improve the signal.

  • Reliable, automatic bypass of failed nodes; dynamic recognition of newly added or removed nodes, with a controller in each port permitting the bypass of a port if the port fails signal validity tests.

  • Active loop reconfiguration when a node to an arbitrated loop is added, removed, or moved.

  • Plug-and-play capability, allowing the hub to connect to compatible servers and other FC-AL devices while they are operating. FC-AL devices can be added or removed while the hub is active.

5.6.2 Shortwave Hub (HP A3724A/AZ)

The short-wave hub supports 10 non-OFC (non- open fiber control) shortwave FC-AL connections. In arbitrated loop topology, the data rates and wavelength between ports must be the same. The shortwave hub supports only gigabit shortwave to gigabit shortwave connections using fiber cables.

For the shortwave hub, Hewlett-Packard recommends 50 micron multimode fiber cable for new installations but supports 62.5 micron multimode fiber cable with SC-style connectors in existing installations. Installations can mix 50 micron and 62.5 micron cables.

Using a 50 micron multimode cable, the short-wave hub supports distances up to 500 meters between a server host and the hub, between a hub port and a connected FC-AL device, and between two hubs. The maximum distance between a host server and FC-AL devices connected to cascaded shortwave hubs is 1500 meters .

5.6.3 Long-wave Hub (HP A4839A/AZ)

The long-wave hub supports nine non-OFC, shortwave devices and a second long-wave FC-AL hub. The long-wave hub supports shortwave gigabit to shortwave gigabit connections from ports 1 through 9 using fiber cables. The long-wave hub also supports a long-wave hub to long-wave hub connection from the long-wave port.

For the long-wave port, Hewlett-Packard recommends 9 micron multimode fiber cable. For ports 1 through 9, Hewlett-Packard recommends 50 micron multimode fiber cable for new installations but supports 62.5 micron multimode fiber cable with SC-style connectors in existing installations.

For ports 1 through 9, the long-wave hub supports distances of 500 meters between the port and a connected FC-AL device. For the long-wave port, the long-wave hub supports distances up to 10 kilometers between two long-wave hubs.

Figure 5-9. Cascaded Long-wave Hub Topology


5.6.4 Plan the FC-AL Connections

The hub does not require drivers or specific versions of the HP-UX operating system, but FC-AL devices that connect to the hub do. Contact an HP sales representative for information on hardware and software requirements for the FC-AL devices you plan to connect to the hub.

  1. Verify the loop cabling configuration is correct by comparing it to the cabling examples in Section Modify the network cabling map as needed.


    Incorrect wiring can lead to problems such as devices left off the loop and inaccessible by the server. Follow the guidelines below before starting.

  2. Review the user -assigned loop ID (hardware address) of every FC-AL device to be connected to the hub and make sure that each ID is unique. Duplicate IDs on the loop can cause problems. In addition, each device has its own factory-assigned unique worldwide name .

  3. Verify the connections between the hub port and the FC-AL mass storage device or the FC-AL adapter are of the same wave type and speed. For example, plan to connect a port on the hub to a shortwave FC-AL device.

  4. Document the planned connections in a cabling map if not already done. Correct Cabling Examples

In a cascaded configuration, connect any port on the first hub to any port on the second hub. The following example includes all 18 nodes in the loop formed by FC-AL Device 1, Hub A, Hub B, and FC-AL Device 2. FC-AL Device 1 is connected to Port 1 on Hub A; Port 10 of Hub A connects to Port 1 of Hub B, and Port 10 on Hub B connects to FC-AL Device 2. In this configuration, Port 10 on Hub B can connect to any FC-AL device. This is just one example of cascaded hubs. The connection between hubs can occupy any combination of ports.

Figure 5-10. Cascaded Shortwave FC-AL Hub Configuration

graphics/05fig10.gif Incorrect Cabling Examples

The following illustrations are examples of incorrect cabling. For example: Do NOT cable together two ports on the same hub. Ports between the two connections will be eliminated from the loop.

Figure 5-11. Incorrect Cabling Example: Connected Ports on the Same Hub


Do NOT attach more than one cable between any two hubs.

Figure 5-12. Incorrect cabling example: more than one cable connection between hubs


Do NOT attempt to connect a hub to more than one other hub.

Figure 5-13. Incorrect cabling example: more than two hubs connected



Fibre Channel for Mass Storage
Fibre Channel for Mass Storage
EAN: 2147483647
Year: 1999
Pages: 53

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