Design Specification; San Topology; Multi-Fabric Sans; Failover Protection - HP StorageWorks 4000/6000/8000 - Enterprise Virtual Arrays Reference Manual

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
Failover protection, page 418
Data access
ISL ratio, page 419
Incremental SAN

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 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
SANs, page 418
patterns, page 418
expansion, page 419
"Data availability" on page 53.