Dell PowerVault MD3000 - Manual (Page 51)

About Your Host
51
I/O Data Path Protection
You can have multiple host-to-array connections for a host. Make sure to
select all of the connections to the array when configuring host access to the
storage array.
NOTICE:
Refer to the Installation Guide for more information on cabling
configurations.
NOTE:
For maximum redundancy, you must select all host connections to the array
when manually defining host topology. For example, a host might have two host
connections. For this host, you would select two host connections.
If a component such as a RAID controller module or a cable fails, or an error
occurs on the data path to the preferred RAID controller module, virtual disk
ownership is moved to the alternate nonpreferred RAID controller module for
processing. This failure or error is called failover.
Multi-path drivers such as MPIO and MPP are installed on host systems that
access the storage array and provide I/O path failover. The multi-path driver
(MPIO in Windows and MPP in Linux) is used for failover. Automatic Virtual
Disk Transfer (AVT) is used specifically for single-port cluster failover. The
AVT feature mode is automatically selected by host type.
NOTE:
You should have the multi-path driver installed on the hosts at all times,
even in a configuration where there is only one path to the storage system, such as
a single port cluster configuration.
During a failover, the virtual disk transfer is logged as a critical event, and an
alert notification is sent automatically if you have configured alert
destinations for the storage array.
Failover with Red Hat Enterprise Linux
For users running Red Hat Enterprise Linux Version 3.0 (x86), the mpp_vhba
failover driver component does not load unless a storage array is connected
and a LUN is mapped to the host server. Follow these steps to ensure proper
MPP driver loading and LUN mapping:
1 Ensure that the storage array is connected to the host server and that out-
of-band (Ethernet) connections to each RAID controller module exist.
2 Create a virtual disk and map it to LUN 0.
3 Reboot the host.