EMC Connectrix EC-1200 Planning Manual page 108

Connectrix Topologies
4
Architecture
4-22
Connectrix v6.02 Planning Guide
ED-1032s, 1 Gb ED-64Ms, DS-16Ms, and DS-32Ms must be set to operate in
Open Fabric mode when they are to be in a fabric with DS-xxBs. (This is an
off-line operation.) If no DS-xxBs will be in the fabric, EMC recommends that
the ED-1032s, 1 Gb ED-64Ms, DS-16Ms, and DS-32Ms be left in McDATA
Fabric mode. This recommendation is based on an the success of more than a
year and a half of shipping directors running in McDATA Fabric mode.
HP-UX FC-SW does not support a Domain ID of 8. (This is documented in
the EMC Support Matrix and HP Fibre Channel Fabric Migration Guide.)
Relative to a typical Ethernet network, an Enterprise Storage
Network has some unique characteristics that can be leveraged for
management and availability objectives.
For example:
A very large percentage of all traffic is server to/from Symmetrix.
On average, there are four to eight times more server ports than
Symmetrix ports.
Symmetrix, tape, and DWDM ports are typically highly shared
resources.
Server to tape I/O is relatively low bandwidth compared to the
bandwidth of the typical network.
There is little to no server-to-server communication.
These characteristics lead to three basic ESN architectures:
Single tier
Two tier
Three tier
Single-Tier Single-tier architecture distributes the Symmetrix ports around the
fabric, locating them near their respective server ports. Zero hops
between the servers and their Symmetrix ports is an advantage. The
design scales with minimal consideration needed for ISL loading. The
disadvantage appears over time if Symmetrix resources are
continuously being reallocated. The logical topology will become
unstructured, exposing the environment to a random number of hops
between the servers and their Symmetrix ports.
A single-tier architecture can compensate by adding ISLs; however, a
fabric of five or more switches requires a large ISL count to
implement a robust full mesh. Some of the loading problems can be
mitigated by moving the Symmetrix ports around the fabric to