Software User Manual

External Storage XP user guide 23
the local array. You must specify the port of a different cluster in the local array for the alternate path, as
ports CL1 and CL2 are specified in the figure.
Figure 2 Example of alternate path configuration
Figure 3 shows another example of an alternate path configuration. In Figure 3, two ports are specified in
the local array and connected to ports in the external array via switches. In this example, two ports from
different XP12000/XP10000/SVS200 clusters are specified in the local array, thereby making it possible
to configure an alternate path for high availability.
Figure 3 Example of alternate path configuration using two switches
In Figure 4, two paths are configured between the internal LDEV and external LU. However, only one port
is specified in the local array and two ports are specified in the external arrays via the switch. Since two
ports of different clusters must be set in the local array for External Storage XP to use alternate path
settings, HP does not recommend the configuration shown in Figure 4.
Figure 4 Example of incorrect alternate path configurations
Examples of switching I/O execution paths to alternate paths
There are two alternate path modes: Single mode and Multi mode. This section describes examples of the
performance when the I/O execution path switches to the alternate path for each path mode.