Red Hat Knowledgebase

When configuring dm_multipath the value of path_grouping_policy is very important. Generally it has two choice: failover and multibus.

The difference between them:
failover - 1 path per priority group
multibus - all valid paths in 1 priority group

When using failover, the output of multipath -ll will be simliar as below:

# multipath -ll mpath3
mpath3 (3600d0230003228bc000339414edb8101)
[size=58 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [prio=1][active]
\_ 2:0:0:6 sdd 8:48 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 3:0:0:6 sdg 8:96 [active][ready]

When using multibus, the output of multipath -ll will be similar as below:

# multipath -ll mpath3
mpath3 (3600d0230003228bc000339414edb8101)
[size=58 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [prio=2][enabled]
\_ 2:0:0:6 sdd 8:48 [active][ready]
\_ 3:0:0:6 sdg 8:96 [active][ready]

Which kind of path_grouping_policy will be chosen, it depends on the storage's feature, but usually multibus can provide round-robin and failover features so it has more advantages than failover.