HP StorageWorks 4000/6000/8000 .HP StorageWorks SAN Design Reference Guide, Pa - Page 57

Table 8 indicates data availability and supported topologies for each level. Table 8 Fabric design data availability Fabric design Availability level SAN topologies Level 1: single connectivity fabric No redundancy Level 2: single resilient fabric Medium Level 3: single resilient fabric with multiple device paths High Level 4: multiple fabrics and device paths (NSPOF) Highest Single switch or multiple switches with single ISL Cascaded with two ISLs, meshed, ring, and core-edge All All You can add fabrics to increase the number of available ports. Table 9 lists the cost calculations for each data availability level. Table 9 Calculating for data availability levels Fabric design Hardware cost Number of available ports Level 1: single connectivity fabric x1 # ports = n - number of ISL ports2 Level 2: single resilient fabric x + additional ISLs # ports = n - number of ISL ports Level 3: single resilient fabric with x + additional ISLs + additional multiple device paths HBAs # ports = n - number of ISL ports - additional HBA ports3 Level 4: multiple fabrics and device paths (NSPOF) x + additional ISLs + additional HBAs + additional switches # ports = 2n - number of ISL ports - additional HBA ports 1x is the cost of a single connectivity fabric. 2n is the total number of ports for servers and storage systems. 3May require use of zoning to define a minimum of two data paths in a single fabric (operating system dependent). SAN Design Reference Guide 57