Configure ALUA Multipath on Centos 5.x with EMC Storage

I am writing more for myself so as not to forget. But suddenly, someone will also be useful.

Faced such a problem. When you register a host in Unisphere you specify failover mode 0.
The system is installed, but not loaded. Multipathd does not start. In the logs we see an entry of the type: “Invalid faliver mode 0”
Putting on the failover mode 1 storage - everything starts

Now the task is to configure active / active instead of active / passive
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We put failover mode 4, in /etc/multipath.conf we add the following text:

devices {
device {
vendor "DGC"
product "*"
prio_callout "/sbin/mpath_prio_alua /dev/%n"
path_grouping_policy group_by_prio
features "1 queue_if_no_path"
failback immediate
hardware_handler "1 alua"
}
}

After that, rebuild the initrd (mkinitrd) and reboot