HP XP P9500 Storage - Manual (Page 22)

NOTE: When you restore a path, use of the restored path is resumed.
Supported external systems’ path mode for external volumes
“Single” or “Multi” path mode displays in Remote Web Console for external volumes on the External
Path Group window. Path modes are based on the external storage system and cannot be changed.
In APLB mode, all paths that are defined are used. I/O operation for external volumes is performed
through load balancing with the use of several paths (round-robin control). External paths connected
to ports in Passive status are not used.
Load Balance Mode
When the path mode of an external volume is Multi or APLB, you can select an I/O control system
for the external storage system.
•
Normal Round-robin: Normal multi-path I/O control system. This distributes I/O to several
paths on which I/O operation is enabled for the external storage system. This mode is applied
to external volumes mapped before 70-04-XX-XX/XX. Specify this if Extended Round-robin
may lower I/O performance. This mode is recommended when the number of sequential I/O
operations is small.
•
Extended Round-robin: Extended multi-path I/O control system. I/O is distributed to several
paths on which I/O operation is enabled for the external storage system. For sequential I/O,
the external volume is divided into sections at regular intervals. In this case, the same path is
used for I/O within the same section which reduces the frequency of I/O distribution. Read
speed can be improved by using the cache function of the external storage system for sequential
22 Requirements and planning