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Appendix A A-11
Fibre Channel Overview
Problems with Fibre Channel
Fibre Channel
Overview
Laser Power Control Systems
There are two types of systems approved for use: OFC and non-OFC.
These two types of control systems can exist on the same network, but
are not optically compatible and cannot be hooked up to the same optical
cable.
Device Addressing
The two modes of addressing used in Fibre Channel, included on page
A-7, are hard and soft addressing. In small, controlled environments,
hard addressing works well. Also, some operating systems and host bus
adapters do not support soft addressing. Large Fabric networks,
connecting many devices, require the flexibility of soft addressing; hard
addressing is not supported in a Fabric environment.
HBA drivers cannot dynamically track device addresses that can change
after the system is turned on. Physical addresses change while the
operating system uses the same logical name for the device. Applications
that always use the same physical device may use the World-Wide Name
(WWN). For example, backup programs must locate the library and all of
its drives regardless of the bus address. Fibre Channel resolves these
issues.
Proper system planning and research prior to installing a Fibre Channel
system will help avoid these problems. Configured properly, Fibre
Channel is as reliable and easy to use as current SCSI systems.