External Storage XP user guide 23
ports from different XP12000/XP10000 clusters are specified in the local disk 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 XP LDEV and external LU. However, only one
port is specified in the local disk array and two ports are specified in the external disk arrays via the
switch. Since two ports of different clusters must be set in the local disk 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.
For more information about path status, see ”Adding alternate paths to multiple external LUs (Add Paths)”
on page 79.
• Alternate path mode is Multi mode
Figure 5 shows an example of when the alternate path mode is Multi mode. When an error occurs in
one path, I/Os execute using paths other than the error path.
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