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Physical Planning Considerations
5
PDCM Array - Example Problem
Figure 5-5
A PDCM array configured for Director A prohibits logical port
address 05 from communicating with logical port addresses 0A, 0B,
and 0C. No PDCM array is configured for Director B. The PDCM
array configured for Director A prohibits the source server from
transmitting or receiving data across ISL 2. However, internal route
tables at both directors indicate a valid server-to-destination device
path across ISL 1.
A problem arises when the source server transmits Class 3 Fibre
Channel data to devices across ISL 1, consuming the ISL bandwidth.
Destination devices are unaware of the PDCM array configured at
Director A and transmit frames back to the server across ISL 2.
Because the server is prohibited from communicating across this ISL,
Class 3 Fibre Channel frames are discarded without generating a
busy (BSY) frame, reject (RJT) frame, or otherwise notifying the
destination devices. The server receives no response from destination
devices and times out. Thus, a server or device failure is indicated,
when in fact the problem is a user-defined prohibited connection.
McDATA Products in a SAN Environment - Planning Manual
5-22
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