Accusys ExaRAID GUI - Manual (Page 189)

Advanced Functions
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5.1.8 Sun Solaris 10 OS Multi-Path Solution
The latest Sun Solaris OS 10 has integrated Storage Multipahting software,
which offers path failover and a path management utility. The single-
controller RAID system is fully compliant with the software. After
configuring the LUN mappings and connecting the RAID system to Solaris
system, you may find multi-path devices in the device directory with their
name of the following format: /dev/dsk/c3t2000002037CD9F72d0s0,
which is largely different from non-multi-path devices, /dev/dsk/c1t1d0s0.
The path management utility, mpathadm, allows you to list paths, list LUN
discovered, configure auto-failover, and control paths. Please check its
man page. For more information about multi-path on Solaris, please refer
to “Solaris Fibre Channel and Storage Multipathing Administration Guide”,
or go to Sun’s online document web site: http://docs.sun.com/, and Sun’s
online forum web: http://wikis.sun.com/.
5.2 Multiple ID solutions
5.2.1 Overview
The multiple ID mechanism provides host transparent controller failover/
failback solution. That is, no particular software or driver is required to be
installed at the host side. Howerver, a fiber switch is required. Through the
connection of fiber switch, the fiber host chanel ports can provide
backup for each other. ‘Fcpa1’ and ‘fcpb1’ can backup each other, so
do ‘fcpa2’ and ‘fcpb2’.
For example, if controller A fails, ‘fcpb1’ inherits the target ID of ‘fcpa1’,
while ‘fcpb2’ inherits the target ID of ‘fcpa2’. When the target ID is
inherited, the lun-map under the ID is inherited as well. Now, both ‘fcpb1’
and ‘fcpb2’ have two IDs. When controller A gets failback, ‘fcpb1’ and
‘fcpb2’ disable the inherited ID before ‘fcpa1’ and ‘fcpa2’ are enabled.
The procedure is delicately controlled to achieve seamless failover/
failback.
When MTID mode is selected, the topology is set to arbitration loop
automatically. The fiber switch ports connected to the RAID fiber ports
should be configured as public loop ports which are often denoted as FL
or GL ports. The target loop ID can be changed manually to avoid
conflict with initiator loop ID if a simple fiber hub is used.
At the moment, only FC RAID system supports multiple ID solutions.