HP StorageWorks 4000/6000/8000 .HP StorageWorks SAN Design Reference Guide, Pa - Page 418

Design specification During the planning process, create a specification that describes your decisions and design. Review and evaluate the design, compare alternatives, make adjustments, and communicate plans before implementation. A complete design specification includes the following elements: • Topology map-Shows the logical SAN topology and fabric interconnect scheme; describes a strategy to accommodate expansion and technological advances • Configuration layout-Shows the physical layout of components; use for troubleshooting and to verify the correct connectivity • Storage map-Defines the storage system configuration and settings, such as host LUN allocation and RAID levels • Zoning map-Defines the communication access settings for devices and user ports in the SAN SAN topology This section describes SAN features for enterprise-level SANs: • Multi-fabric SANs, page 418 • Failover protection, page 418 • Data access patterns, page 418 • ISL ratio, page 419 • Incremental SAN expansion, page 419 Multi-fabric SANs HP recommends using two or more separate fabrics for enterprise-level SANs. Multiple fabrics protect against potential failure points, such as hardware, software, or operator error. The failure of one fabric does not affect other fabrics in the SAN. Failover protection Use failover technology in SAN configurations that have two or more fabrics. Each server has two or more HBAs. If the communication path from one HBA to the storage system fails, the I/O traffic is rerouted through the other HBA. To minimize the risk of uneven workloads, configure the separate fabrics for similar size and topology. You can also use failover protection in SANs with only one fabric to protect against HBA, path, and storage controller failures. For more information, see "Data availability" on page 53. Data access patterns Review your data access needs before making a topology choice. The optimum SAN configuration depends on I/O traffic requirements and data access patterns: • Local (one-to-one)-Data access between a local server and a storage system connected to the same switch • Centralized (many-to-one)-Data access between multiple, dispersed servers and one centrally located storage system 418 Best practices