HP StorageWorks 4000/6000/8000 - Enterprise Virtual Arrays, Справочное руководство

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Level 4: multiple fabrics and device paths (NSPOF)
Level 4 provides multiple data paths between servers and storage systems, but unlike level 3, the paths
connect to physically separate fabrics (
Figure 15 ). This level ensures the highest availability with
NSPOF protection. If a switch, server HBA, or storage system path failure occurs, data is automatically
rerouted through the alternate fabric and there is no interruption in server I/O activity.
Level 4 minimizes vulnerability to fabric failures (for example, improper switch replacement, incorrect
fabric configuration settings, or a fabric service failure). Level 4 also provides the highest level of
performance and a higher number of available ports, since all fabrics can be accessed simultaneously
during normal operations.
25101a
A B
Figure 15 Level 4: multiple fabrics and device paths (NSPOF)
.
Using two fabrics may increase implementation costs, but it also increases the total number of available
ports. For example, in a single meshed fabric with four switches, you have a maximum of 52 user
ports for servers and storage. Implementing the same topology using two fabrics increases the maximum
number of user ports to 104.
Considerations
When choosing a data availability level, you must consider:
• Cost
• Access to critical data
For mission-critical applications, HP recommends that you implement a level 4, fully redundant fabric
configuration. You can justify the additional cost if you consider the cost of losing access to critical
data.
SAN fabric topologies 56