Red Hat DEVICE-MAPPER MULTIPATH 4.6 Configuration And Administration Manual page 12

Chapter 1. Device Mapper Multipathing
Figure 1.1. Active/Passive Multipath Configuration with One RAID Device
In this configuration, there is one I/O path that goes through hba1, SAN1, and controller 1 and a
second I/O path that goes through hba2, SAN2, and controller2. There are many points of
possible failure in this configuration:
• HBA failure
• FC cable failure
• SAN switch failure
• Array controller port failure
With DM-Multipath configured, a failure at any of these points will cause DM-Multipath to switch
to the alternate I/O path.
Figure 1.2, "Active/Passive Multipath Configuration with Two RAID Devices" shows a more
complex active/passive configuration with 2 HBAs on the server, 2 SAN switches, and 2 RAID
devices with 2 RAID controllers each.
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