EMC Connectrix EC-1200 Planning Manual page 78

Zoning and Naming
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An HBA in a single-HBA zone on an ED-140M or ED-64M sees only
the State Change Notifications (SCNs) of the Symmetrix storage ports
configured for the adapter. As the fabric scales to a larger number of
ports, the device discovery process and the response to SCNs is not
lengthened or complicated.
Volume Logix works in concert with single-HBA zoning. Volume
Logix operates at the volume level, granting volume access only to
those HBAs that have the appropriate permissions.
Volume Logix does not operate at the switch port level, and as a
result does not directly control the storage port discovery process.
Without single-HBA zoning in a Volume Logix environment, the
HBAs will attempt to log in to all ports on the fabric during discovery
and during the HBA's response to an SCN. By using single-HBA
zoning with Volume Logix, the time and Fibre Channel traffic used to
process discovery and SCN is held to a minimum, increasing the
speed, efficiency, and reliability of the fabric.
In a consolidation topology with a four-to-one fan-out, there are four
zones, one for each HBA. The shared Symmetrix port is a member of
each zone. Also, if an HBA will access multiple Symmetrix ports, that
HBA's zone will include all of the WWPNs of those Symmetrix ports.
Single-HBA zoning will effectively migrate from a single switch to a
multiswitch environment. By building zones with World Wide
Names, it does not matter where in the fabric an N_Port attaches. The
distributed Name Server will adjust automatically, making these
physical topology changes transparent to the configuration variables
of the device drivers.
CAUTION
!
The single-HBA zoning capability depends on FC-SW
functionality in the device driver. This capability is supported by
the EMC-approved Solaris, Windows NT, and AIX device drivers.
Not all future device drivers may support this capability. Check
your driver's manual for FC-SW configuration restrictions.
Field experimentation with multiple HBAs in the same zone
haslogged in to yielded benign and negative results depending on the
environment. If n HBAs are added to a single zone, each time an
RSCN is propagated in that zone there will be (n * (n-1) ) useless
PLOGIs/Rejects, impeding the completion of the RSCN processing.
The approach does not scale with positive results.
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Connectrix v6.02 Planning Guide