HP StorageWorks External Storage XP user guide (December 2005)

14 External Storage XP for the XP10000/XP12000
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. The following sections describe
examples of the performance when the I/O execution path is switched to the alternate path for each path
mode:
• ”Alternate path mode is Multi mode” on page 14
• ”Alternate path mode is Single mode” on page 15
• ”Alternate path mode is Single mode and at least one alternate path is in Standby status” on page 16
For more information about path status, see ”Setting alternate paths on each external LU” on page 57.
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.