HP Surestore 64 FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availabil - Page 108
FCP and FICON in a Single Fabric
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Planning Considerations for Fibre Channel Topologies ■ Employ a routing protocol to establish the shortest path through the fabric and program route tables for each fabric element. ■ Exchange the active zone set to ensure uniform zoning is enforced between all fabric elements. However, fabric initialization is not a serial process. The process executes concurrently across all ISLs in the fabric, causing a massive flood of Class F traffic that must processed to the embedded port of each fabric element within a specified (fabric-wide) error detect time- out value (E_D_TOV). If the fabric consists of a large number of elements (and therefore ISLs), Class F traffic may not be processed within the E_D_TOV, resulting in error recovery operations, timeouts, segmented links, or fabric failure. Because of these problems, a fabric with a high ISL count is more difficult to build. Note that the fabric problem is not directly related to the large number of fabric elements, but to the large number of ISLs associated with the elements. Fabric build concerns currently limit the combined number of directors and switches to about 24. FCP and FICON in a Single Fabric Fibre Channel Layer 4 (FC-4) describes the interface between Fibre Channel and various upper-level protocols. FCP and FICON are the major FC-4 protocols. FCP is the Fibre Channel protocol that supports the small computer system interface (SCSI) upper-level transport protocol. FICON is the IBM successor to the enterprise systems connection (ESCON) protocol, and adds increased reliability and integrity to that provided by the FCP protocol. Because FCP and FICON are both FC-4 protocols, routing of Fibre Channel frames is not affected when the protocols are mixed in a single fabric environment. However, management differences in the protocols arise when a user changes director or edge switch parameters through zoning or connectivity control. In particular: ■ FCP communication parameters are port number and name-centric, discovery oriented, and assigned by the fabric, and they use the Fibre Channel name server to control device communication. ■ FICON communication parameters are logical port address-centric, definition oriented, and assigned by the attached host, and they use host assignment to control device communication. 108 SAN High Availability Planning Guide