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 or more connections)
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Example 1
In a 4-path connection, when one of two active paths becomes unavailable, processing continues on the
remaining active path. Switching to the standby path is not performed because the CM still has one active
path available.
Figure 3.6 4-path failover, active to active
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Example 2
If both active paths for a CM become unavailable, a standby path is then switched to active state to
continue processing. When there are two or more standby paths, load balancing is also performed.
Figure 3.7 4-path failover, active to standby
Multipath Driver
LU0
I/O request
Storage system with CM assigned (4-path or more)
HBA #0
HBA #1
HBA #2
CM #0
CM #1
HBA #3
Linux server
Failure
Active path Active path
Multipath Driver
LU0
I/O request
Storage system with CM assigned (4-path or more)
HBA #0
CM #0
Linux server
Active path
CM #1
HBA #2
HBA #3
HBA #1
Standby path
Standby path
Active path
Failure
