1.1. Overview of DM-Multipath

1.1. Overview of DM-Multipath

DM-Multipath can be used to provide:

Figure 1.1, “Active/Passive Multipath Configuration with One RAID Device” shows an active/passive configuration with two I/O paths from the server to a RAID device. There are 2 HBAs on the server, 2 SAN switches, and 2 RAID controllers.

Active/Passive Multipath Configuration with One RAID Device

Active/Passive Multipath Configuration with One RAID Device

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:

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.

Active/Passive Multipath Configuration with Two RAID Devices

Active/Passive Multipath Configuration with Two RAID Devices

Figure 1.2. Active/Passive Multipath Configuration with Two RAID Devices

In the example shown in Figure 1.2, “Active/Passive Multipath Configuration with Two RAID Devices”, there are two I/O paths to each RAID device (just as there are in the example shown in Figure 1.1, “Active/Passive Multipath Configuration with One 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:

In this configuration, I/O can be spread among those four paths.

Active/Active Multipath Configuration with One RAID Device

Active/Active Multipath Configuration with One RAID Device

Figure 1.3. Active/Active Multipath Configuration with One RAID Device


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