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In Figure 2-5, two paths are also set between the internal volume and the
external volume. However, one port is specified in the local storage system,
and two ports are specified in the external storage systems over the switch.
This configuration is not recommended because two ports of different clusters
need to be set in the local storage system for alternate path settings in
Universal Volume Manager.
Local Storage System
Internal
Volume
Legend
Figure 2-5
Examples of Switching I/O Execution Paths to Alternate Paths
This section describes the case examples of the performance when the I/O
execution path is switched to the alternate path for each path mode as
follows:
–
When the path mode is Multi mode
–
When the path mode is Single mode
–
When the path mode is Single mode and there is at least one alternate
path in the Standby status
•
When the path mode is Multi mode
Figure 2-6 shows an example of the case when the path mode is Multi
mode. When an error occurs in one path, I/Os are executed using the
paths other than the error path.
Note: As you restore the error path, the use of the restored path is
automatically resumed.
2-14
Hitachi Universal Storage Platform V/VM Universal Volume Manager User's Guide
External
CL1-A
：Internal volume where the external volume is mapped
Example of Unavailable Alternate Path Setting
About Universal Volume Manager Operations
External Storage System
Switch
Port
Path 1
WWN A
Port
Path 2
WWN B
LUN
5
External
Volume
LUN
5
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