Multipath Connectivity

UltraPath is a Huawei-developed multipathing software. It can manage and process disk creation/deletion and I/O delivery of operating systems.

UltraPath provides the following functions:

• Masking of redundant LUNs

  In a redundant storage network, an application server with no multipathing software detects a LUN on each path. Therefore, a LUN mapped through multiple paths is mistaken for two or more different LUNs. UltraPath installed on the application server masks redundant LUNs on the operating system driver layer to provide the application server with only one available LUN, the virtual LUN. In this case, the application server only needs to deliver data read and write operations to UltraPath that masks the redundant LUNs, and properly writes data into LUNs without damaging other data.

• Optimum path selection

  In a multipath environment, an application server with UltraPath accesses a LUN on the storage system through an optimum path, thereby obtaining the highest I/O speed.

• Failover and failback
  • Failover

    When a path fails, UltraPath fails over its services to another functional path.

  • Failback

    UltraPath automatically delivers I/Os to the first path again after the path recovers from the fault.

• I/O Load balancing

  UltraPath provides load balancing within a controller and across controllers.

  • For load balancing within a controller, I/Os poll among all the paths of the controller.
  • For load balancing across controllers, I/Os poll among the paths of all these controllers.
• Path test

  UltraPath tests the following paths:

  • Faulty paths

    UltraPath tests faulty paths with a high frequency to detect the path recover as soon as possible.

  • Idle paths

    UltraPath tests idle paths to identify faulty paths in advance, preventing unnecessary I/O retries. The test frequency is kept low to minimize impact on service I/Os.

DM-Multipath is the native multipathing software in SUSE.

DM-Multipath allows you to configure multiple I/O paths between a host and a storage system as one device. These I/O paths may contain independent physical devices such as cables, switches, and controllers.

DM-Multipath supports redundant paths and improves system performance.

• Redundancy

  DM-Multipath supports active/standby path configuration. This configuration creates a redundant path for each active path. The redundant paths are not used when the active paths work properly. Once an element (such as a cable, switch, or controller) on an active I/O path becomes faulty, DM-Multipath switches I/Os to a standby path.

• Performance enhancement

  DM-Multipath supports active-active paths, that is, I/Os are distributed to all paths based on the I/O scheduling algorithm. DM-Multipath can check I/O loads on paths and dynamically balance I/Os among the paths using the round-robin algorithm.

Table 2-1 describes DM-Multipath components.