Failover Policy - Brocade Communications Systems A7533A - Brocade 4Gb SAN Switch Base Administrator's Manual

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Failover policy

Failover policy

Access Gateway Failover and Failback policies ensure maximum uptime for the servers. When a
port is configured as an N_Port and if by default, the Failover policy is enabled, F_Ports are not
disabled if its N_Port goes off line. If you specify a Preferred Secondary N_Port for any of the
F_Ports, and if the N_Port goes offline, the F_Ports will fail over to the Preferred Secondary N_Port,
and then re-enable. The specified Preferred Secondary N_Port must be online; otherwise, the
F_Ports will become disabled.
Alternatively, if a Preferred Secondary N_Port is not set for any of F_Ports, the F_Ports will fail over
to other online N_Ports belonging to the same N_Port group, and then re-enable. The FLOGI and
FDISC requests are forwarded from F_Ports through the new N_Port. If multiple N_Ports are
available as candidates for failover, Access Gateway selects one or more N_Ports so that the
F_Ports are evenly balanced across all the N_Ports.
NOTE
Failover of F_Ports to new a N_Port generates a RASLOG message.
The Failover policy allows hosts to automatically remap to an online N_Port if the primary N_Port
goes offline. The Failover policy is enabled (or enforced) during power-up. The Failover policy evenly
distributes the F_Ports that are mapped to an offline N_Port among all the online N_Ports. The
Failover policy is a parameter of each N_Port. By default, the Failover policy is enabled for all
N_Ports.
The following sequence describes how a failover event occurs:
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Example: Failover Policy
This example shows the failover behavior in a scenario where two fabric ports go offline, one after
the other. Note that this example assumes that no Preferred Secondary N_Port is set for any of the
F_Ports.
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An N_Port goes offline.
All F_Ports mapped to that N_Port are disabled.
If the N_Port Failover policy is enabled, and a Preferred Secondary N_Port is specified for the
F_Port and that N_Port is online, the F_Port fails over to the respective Preferred Secondary
N_Port, and then re-enables.
NOTE
The Preferred Secondary N_Port is defined per F_Port. For example, if two F_Ports are mapped
to a primary N_Port1, you can define a secondary N_Port for one of those F_Ports and not
define a secondary N_Port for the other F_Port. Typically, this is done by the server
administrator. You must determine whether you want to define a preferred secondary map for
each of the servers or just a subset of the servers.
If the Preferred Secondary N_Port is not online, those F_Ports are disabled.
If the Preferred Secondary N_Port is not set for any of the F_Ports, those F_Ports will fail over
to other available N_Ports belonging to the same N_Port group, and then re-enable.
The host establishes a new connection with the fabric.
First the Edge switch F_A1 port goes offline, as shown in
causing the corresponding Access Gateway N_1 port to be disabled.
The ports mapped to N_1 fail over; F_1 fails over to N_2 and F_2 fails over to N_3.
Figure 4 on page 15 Example 1 (left),
Access Gateway Administrator's Guide
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