.SAN design reference guide Vol. 1-5 785350-001

Ring fabric expansion
Expand a ring fabric by adding a switch to the ring.
Add new switches cascaded off the ring, up to the maximum number of switches supported in a
single fabric. When expanding outside the ring, ensure that communicating devices are connected
by no more than seven hops.
Core-edge fabric expansion
Expand a core-edge SAN fabric by adding edge switches. Connect edge switches to available
ports on the backbone switches.
If the current SAN contains only one core switch, add another. Connect edge switches to ports on
the new core switch.
SAN fabric merging
You can merge independent fabrics into a single, larger fabric. Merging enables you to:
• Provide more resources to independent SAN fabrics.
• Share the resources in two or more fabrics.
• Make information in one SAN available to servers in another SAN.
• Connect geographically dispersed fabrics into a single SAN.
During initial login, the discovery process determines whether the fabrics are compatible. If not,
segmentation occurs and they continue to operate as separate fabrics. See “Fabric segmentation
errors” (page 403).
When fabrics merge, the zone configuration databases are updated to include the zone
configurations of each fabric. If a nonzoned fabric merges with a zoned fabric, all zoning
information is proliferated to the nonzoned fabric switches. A zone configuration that is enabled
at the time of the merge is also enabled on the nonzoned fabric switches. Devices in the nonzoned
fabric are not accessible until you add them to the current configuration.
NOTE: When enabling a new configuration, HP strongly recommends that the fabric be quiesced.
Zone membership should not be changed for devices that are actively performing I/O in a fabric.
Once the new zoning is enabled, an RSCN is sent to all nodes that have been registered to receive
the RSCN.
The following sections provide information to help you successfully merge SAN fabrics:
• “Fabric segmentation errors” (page 403)
• “Switch configuration parameters” (page 403)
• “Independent fabric merge” (page 403)
• “High-availability redundant fabric merge” (page 403)
402 Best practices