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Planning Considerations for Fibre Channel Topologies
3
SAN Islands
Planning for Multiswitch Fabric Support
McDATA Products in a SAN Environment - Planning Manual
3-18
•
Tier 2 - A Tier 2 device connects to an edge switch and Fibre
Channel traffic from the device must traverse only one ISL (hop)
to reach a device attached to a core director or switch.
•
Tier 3 - A Tier 3 device connects to an edge switch and Fibre
Channel traffic from the device can traverse two ISLs (hops) to
reach a device attached to a core director or switch.
A SAN island is an isolated or geographically diverse Fibre Channel
fabric. These fabrics may also comprise different topologies (mesh or
core-to-edge), but may require connectivity for shared data access,
resource consolidation, data backup, remote mirroring, or disaster
recovery.
When connecting multiple fabrics, data traffic patterns and fabric
performance requirements must be well known. Fabric island
connectivity must adhere to topology limits, including maximum
number of fabric elements and ISL hop count. It is also essential to
maintain data locality within fabric islands as much as possible and
to closely monitor bandwidth usage between the fabric islands. Refer
to
SAN Island Consolidation
A Fibre Channel topology that consists of one or more interconnected
director or switch elements is called a fabric. The product operational
software provides the ability to interconnect directors and switches
(through E_Port connections) to form a multiswitch fabric. Support of
multiswitch fabric operation is a major feature of a director or fabric
switch. Consider installation of multiple directors or switches to form
a high-availability fabric topology that supports multiple, full-
bandwidth data transmission paths between servers and devices.
Figure 3-11
illustrates a simple multiswitch fabric. In the figure, the
three fabric elements are Intrepid 6064 Directors.
Fabric elements cooperate to receive data from the N_Port of an
attached device, route the data through the proper director or switch
fabric ports (F_Ports), and deliver the data to the N_Port of a
destination device. The data transmission path through the fabric is
typically determined by the fabric elements and is transparent to the
user. Subject to zoning restrictions, devices attached to any of the
interconnected directors or switches can communicate with each
other through the fabric.
for additional information.
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