Multipath is working

Yesterday, we got multipath working with our HP MSA1500cs SAN. We have a fully redundant setup with redundant controllers, fibre channel switches, and two FC controllers per host.

We had been having a lot of trouble getting things to work right with active/passive controllers. We could get failover to work in some cases, but getting everything to communicate correctly in the event of a failure was difficult, since every machine would have to flip over to the passive controller simultaneously.

With a firmware upgrade, the MSA 1500cs can support active/active controllers. With the dual-active setup, both controllers are active simultaneously and both are valid paths.

Despite HP support’s indications to the contrary, HP does have information on using built-in multipathd in Linux instead of their proprietary multipath solution. It’s document c00635587, part AA-RW8RA-TE.

We’ve configured multipathd.conf like this:

      path_grouping_policy  multibus
      path_checker              tur
      failback                  immediate
      no_path_retry             60
      path_selector             "round-robin 0"

Just put that in your default block and it should work.

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