Chapter 3 Multipath Driver Functions and Operation
3.2 Load Balancing/Failover
FUJITSU Storage ETERNUS Multipath Driver V2 User’s Guide for Linux
Copyright 2014 FUJITSU LIMITED
P2U3-0031-15ENZ0
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3.2
Load Balancing/Failover
There are two types of storage systems. The first is a storage system whose access paths are assigned to one of
the two CMs (hereinafter referred to as "storage system with CM assigned"), the second is a storage system
whose access paths are not assigned to a particular CM
(hereinafter referred to as "storage system with CM not assigned").
In the storage system with CM assigned, paths that belong to the assigned CM are active and other paths
connected to non-assigned CM are standby.
In the storage system with CM not assigned, all paths are active, and used to access data.
Load balance and failover control operations vary according to the storage system type (whether the storage
system has assigned CM or not) and number of paths.
For details on which storage systems have assigned CMs or not are provided in the "FUJITSU Storage ETERNUS
Multipath Driver V2 (for Linux) Installation Information" found under "Downloads" at the following URL:
http://www.fujitsu.com/global/products/computing/storage/software/eternus-mpd/
3.2.1
Load Balancing
The Multipath Driver uses all active paths to perform load balancing (load distribution) to improve
performance.
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Storage system with CM assigned (2 path connections)
For a storage system with CM assigned (2-path) connection, one path is connected to each controller.
Of the two paths, the path connected to the assigned CM is active and the path connected to the non-
assigned CM is on standby. If there is only one active path, load balancing is not performed.
Figure 3.2 2-path load balancing on a storage system with CM assigned
Storage system with CM assigned (2-path)
Linux server
Multipath Driver
I/O request
LUN0
LUN1
CM #0
CM #1
HBA #0
HBA #1
