Specifications

DATA CENTER BEST PRACTICES
SAN Design and Best Practices 15 of 84
Brocade recommends core-edge or edge-core-edge as the primary SAN design methodology, or mesh topologies
used for small fabrics (under 2000 ports). As a SAN design best practice, edge switches should connect to at
least two core switches with trunks of at least two ISLs each. Each of those trunks should be attached to a
different blade/port group. In order to be completely redundant, there would be a completely mirrored second
fabric and devices need to be connected to both fabrics, utilizing MPIO.
Recommendations for switch ISL/UltraScale ICL connectivity are:
•There should be at least two core switches.
• Every edge switch should have at least two trunks to each core switch.
•Select small trunk groups (keep trunks to two ISLs) unless you anticipate very high trafc volumes. This
ensures that you can lose a trunk member without losing ISL connectivity.
•Place redundant links on separate blades.
•Trunks should be in a port group (ports within an ASIC boundary).
•Allow no more than 30m in cable difference for optimal performance for ISL trunks.
•Use the same cable length for all UltraScale ICL connections.
•Avoid using ISLs to the same domain if there are UltraScale ICL connections.
•Use the same type of optics on both sides of the trunks: Short Wavelength (SWL), Long Wavelength (LWL), or
Extended Long Wavelength (ELWL).
Device Placement
Device placement is a balance between trafc isolation, scalability, manageability and serviceability. With the
growth of virtualization and multinode clustering on the UNIX platform, frame congestion can become a serious
concern in the fabric if there are interoperability issues with the end devices.
Trafc Locality
Designing device connectivity depends a great deal on the expected data ow between devices. For simplicity,
communicating hosts and targets can be attached to the same switch.
fig09_SAN_Design
Data
Flow
Data
Flow
Minimal Data Flow
Figure 9. Hosts and targets attached to the same switch to maximize locality of data ow.