Why "rr_min_io" option in /etc/multipathd.conf is ignored?

Issue

• Cannot set rr_min_io in /etc/multipathd.conf - setting is ignored
• We have RHEL 5.5 running on a Cisco UCS B250, connected to an EMC VMAX.

We set the rr_min_io lower than the default (1000). After setting this option , "multipath -v3 | grep minio" command still show default minio:

[root@test ~]# multipath -v3 | grep minio
360000970000192604211533035383330: minio = 1000 (controller setting)
360000970000192604211533035383334: minio = 1000 (controller setting)
360000970000192604211533035313832: minio = 1000 (controller setting)
360000970000192604211533035383234: minio = 1000 (controller setting)
360000970000192604211533035383238: minio = 1000 (controller setting)
360000970000192604211533035383243: minio = 1000 (controller setting)
mpath0: minio = 1000 (controller setting)
360000970000192604211533035313736: minio = 1000 (controller setting)

We have changed rr_min_io to 16 and then re-run multipath, but nothing we do changes the setting, including rebooting the system.