IBM TotalStorage DS300 Best Practices Manual page 440

device-mapper (in our setup we use device-mapper-1.01.01-1.2, which is
shipped with SP2 - check for the current version)
multipath-tools (in our setup we use multipath-tools-0.4.4-0.22, which is
shipped with SP2 - check for the current version)
To get a working DM MPIO configuration for linux-iscsi, the configuration file
/etc/iscsi.conf needs additional parameters as shown in Example 7-7. Again, the
shown configuration can be used to ensure that the setup works, but should not
be used for production use as it lacks any security configuration.
Example 7-7 initial /etc/iscsi.conf for multipath IO
DiscoveryAddress=192.168.1.61
Multipath=portal
ConnFailTimeout=10
With Multipath=portal, linux-iscsi establishes iSCSI sessions to the target using
each of the network portals in the target. Each session is bound to a different
SCSI address in /proc/scsi/scsi. This will lead to two block devices (sdb and sdc)
for the single logical drive in our example.
ConnFailTimeout=10 is necessary to fail SCSI commands after 10 Seconds. The
value depends on your needs and on your network setup. The default value for
ConnFailTimeout is 0, which means no timeout. The timeout is necessary to
notify device mapper about a failed path.
Important: ConnFailTimeout=10 ensures a quick failover in case a network
path from the server to the switch fails. If a controller failover in the DS300
happens, ConnFailTimeout=10 will lead to both paths failing as the controller
failover takes longer than 10 seconds (see 3.3.5, "DS300 failover" on
page 41). In this example we handle this with the queue_if_no_path setting in
/etc/multipath.conf.
When starting linux-iscsi with this configuration, the log information changes
compared to the single path IO configuration as shown in Figure 7-308 on
page 423.
422
IBM TotalStorage DS300 and DS400 Best Practices Guide