HP Mainframe Connectivity Design Guide

Topology data access
To select a FICON SAN fabric topology, you must determine which data access type is appropriate
for your environment. The data access types are as follows:
• Local (one-to-one)—Data access between a local server and a storage system connected to
the same director
• Centralized (many-to-one)—Data access between multiple, dispersed servers and one centrally
located storage system
• Distributed (many-to-many)—Data access between multiple, dispersed servers and storage
systems
• Centralized (one-to-many)—Data access between one centrally located server and multiple,
nl
dispersed storage systems
NOTE: In general, increasing the number of FICON ports on the mainframe and/or storage
system improves performance and reduces data access times. FICON allows up to eight channel
paths from an LPAR to each storage system CU or LCU.
Table 2 (page 19) lists the data access performance ratings for each SAN fabric topology.
Table 2 Data access performance by SAN fabric topology
Data access performance
SAN topology DistributedCentralizedLocal
HighestHighestHighestSingle-switch fabric
HighHighHighestCascaded fabric
1
1
Provided that the ISLs meet the data throughput required by the mainframe and storage system
Data availability
Data availability depends on the reliability of the FICON SAN fabric, mainframes, and storage
systems during routine operations. The data availability level required for your SAN environment
is based on the following:
• Administrative requirements (for example, backup schedules, operating procedures, and
staffing)
• Protection level for applications or data
• Hardware redundancy
Factors
Several factors affect SAN data availability:
• Application software
• Mainframe operating systems
• Mainframe hardware
• Number of CHPIDs connected to the SAN
• SAN fabric infrastructure
• Primary and secondary storage
• Number of storage system FICON ports connected to the SAN
• Number of FICON directors
• Number of ISLs
Topology data access 19