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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Storage system with CM assigned (4 path connections)
For a storage system with a 4-path configuration, two paths are connected to each of the two CMs, for a total
of four paths.
The two paths connected to the assigned CM are active, and load balance control is executed on these two
paths.
For an 8-path configuration, two paths are connected to each of the four CMs, for a total of eight paths.
Figure 3.3 4-path load balancing on a storage system with CM assigned
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Storage system with CM not assigned
For a storage system that does not have an assigned CM, there is no concept of standby path, so all connected
paths are active, and load balancing is performed over all paths.
Figure 3.4 Multipath load balancing on a storage system with CM not assigned
Multipath Driver
LU0
I/O request
LU1
Storage system with CM assigned (4-path)
HBA #0
HBA #1
HBA #2
HBA #3
CM #0
CM #1
LU1
Load balance
LU0
Load balance
Linux server
Multipath Driver
LU0
I/O request
LU1
Storage system with CM not assigned
HBA #3
HBA #0
HBA #1
CM #0
HBA #2
CM #1
LUN0/1 Load balance
Linux server
