||Oracle Tips by Burleson
Disk I/O Tuning
energized, each NL_Port signs in with the other ports on its loop.
The NL_Port will first attempt to locate an FL_Port. If the NL_Port
finds an FL_Port, it knows it is attached to a public loop connected
to a fabric. If the port does not locate an FL_Port, it then knows
it is a part of a private loop with other NL_Ports only.
can be up to 126 active NL_Ports and up to one active FL_Port
attached to the same arbitrated loop. If for some reason an NL_Port
does not attempt to discover an FL_Port and there is an FL_Port
present, the NL_Port is only allowed to access other NL_Ports on the
are usually equipped with port bypass circuitry that allows the port
to be bypassed when it is malfunctioning or a device in a loop has
been removed. These are known as PBCs and are generally located
external to the drives or devices.
provide an analogy, a SCSI chain is like a neighborhood, the fibre
channel acts as the highway connecting multiple neighborhoods.
that we have looked at the various disk interface technologies, in
the next chapter we will look at some basic ways to optimize them.
The above text is
an excerpt from:
Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle
by Mike Ault
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