Installation guide

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 T wo 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.
Figure 1.2. Act ive/Passive Multipath Configurat ion with Two RAID Devices
As in the example shown in Figure 1.1, “Active/Passive Multipath Configuration with One RAID Device”,
there are two I/O paths to each RAID device. With DM-Multipath configured, a failure at any of the points
of the I/O path to either of the RAID devices will cause DM-Multipath to switch to the alternate I/O path for
that device.
Figure 1.3, “Active/Active Multipath Configuration with One RAID Device” shows an active/active
configuration with 2 HBAs on the server, 1 SAN switch, and 2 RAID controllers. There are four I/O paths
from the server to a storage device:
hba1 to controller1
hba1 to controller2
hba2 to controller1
hba2 to controller2
In this configuration, I/O can be spread among those four paths.
Chapter 1. Device Mapper Multipathing
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