.Part 1 Architecture HP SAN Design Reference Guide 785351-001

Data availability
SAN data availability depends on the reliability of the SAN fabric, servers, and storage systems
during routine operations. The data availability level required for your SAN environment is based
on:
• Administrative requirements (for example, backup schedules, operating procedures, and
staffing)
• Protection level for applications or data
• Hardware redundancy
NOTE: For more information about high-availability configurations when using the HP B-series
MP Routers or C-series VSANs, see “High-availability router configurations” (page 55).
Several factors affect SAN data availability:
• Application software
• Server operating systems
• Server hardware
• SAN fabric infrastructure
• Primary and secondary storage
• Number of switches
• Number of ISLs
• Number of paths between a server or clustered servers and the fabric
• Number of storage controller paths in the fabric
Levels
This section describes the data availability levels.
Level 1: single connectivity fabric
Level 1 provides maximum connectivity but does not provide fabric resiliency or redundancy. Each
switch has one path to other switches in the fabric (Figure 10). Each server and storage system
has one path to the fabric.
Figure 10 Level 1: single connectivity fabric
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Level 2: single resilient fabric
Level 2 provides fabric path redundancy by using multiple ISLs between switches (Figure 11). Each
server and storage system has one path to the fabric. If an ISL or switch port failure occurs, the
38 SAN fabric topologies