Why Device Mapper Multipath failing to create maps for boot from SAN disk in RHEL 6/7?

Issue

• Server is booting from single scsi path, multipath devices not getting created. multipath -ll does not return any paths?
• I'm trying to configure BootOnSan on my server Red Hat Enterprise Linux on EMC. The problem I have is that multipath -ll command don't return anything.
• Hereunder, you will find the /etc/multipath.conf file I use and another commands :

# cat /etc/multipath.conf
defaults {
        find_multipaths yes
        user_friendly_names yes
}
blacklist {
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^hd[a-z][[0-9]*]"
        devnode "^cciss!c[0-9]d[0-9]*"
}
devices {
        device {
                vendor "DGC"
                product "*"
                prio tpg_pref
                path_grouping_policy group_by_prio
                features "1 queue_if_no_path"
                failback immediate
                hardware_handler "1 alua"
        }
}

[root@localhost ~]# multipath -ll
[root@localhost ~]# multipath -l 
[root@localhost ~]# multipath -d
create: mpatha (3600601608db038002f6972087458e511) undef DGC,VRAID
size=50G features='1 queue_if_no_path' hwhandler='1 alua' wp=undef
|-+- policy='round-robin 0' prio=130 status=undef
| `- 2:0:1:0 sdb 8:16 undef ready running
`-+- policy='round-robin 0' prio=10 status=undef
  `- 2:0:0:0 sda 8:0  undef ready running