1.2. Overview of DM Multipath

DM Multipath can be used to provide:

이중화
DM Multipath can provide failover in an active/passive configuration. In an active/passive configuration, only half the paths are used at any time for I/O. If any element of an I/O path (the cable, switch, or controller) fails, DM Multipath switches to an alternate path.
성능 향상
DM Multipath can be configured in active/active mode, where I/O is spread over the paths in a round-robin fashion. In some configurations, DM Multipath can detect loading on the I/O paths and dynamically rebalance the load.

그림 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.

그림 1.1. Active/Passive Multipath Configuration with One RAID Device

이 설정에서, hba1, SAN1, 제어기 1을 통해 지나가는 첫 번째 I/O 경로와 hba2, SAN2, 제어기 2를 통해 지나가는 두 번째 I/O 경로가 있습니다. 이러한 설정에는 장애가 발생할 수 있는 지점이 여러개 있습니다.

With DM Multipath configured, a failure at any of these points will cause DM Multipath to switch to the alternate I/O path.

그림 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.

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

In the example shown in 그림 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 그림 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.

그림 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:

설정에서 I/O는 이러한 네 개의 경로 중 배치될 수 있습니다.

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