Upgrade And Downgrade Considerations For Failover; Failback; Failback Configurations In Access Gateway - Brocade Communications Systems 8 Administrator's Manual

3

Failback

3. Enter the ag

Upgrade and downgrade considerations for Failover

Consider the following when upgrading or downgrading Fabric OS versions.
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Failback

Failback policy provides a means for hosts that have failed over to automatically reroute back to
their intended mapped N_Ports when these N_Ports come back online. Failback policy is an
attribute of an N_Port and is enabled by default when a port is locked to the N_Port.
Only the originally mapped F_Ports fail back. In the case of multiple N_Port failures, only F_Ports
that were mapped to a recovered N_Port experience failback. The remaining F_Ports are not
redistributed.
NOTE
For port-based mapping, the Failback policy must be enabled on an N_Port for failback to occur. For
device-based mapping, the Failback policy has no effect. If a device is mapped to a port group, it will
always fail over to an online N_Port in the port group (or secondary N_Port if configured) and will
remain connected to this failover N_Port when the original N_Port comes back online.

Failback configurations in Access Gateway

The following sequence describes how a failback event occurs:
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NOTE
The failback period is quite fast and rarely causes an I/O error at the application level.
Example : Failback
In Example 3, described in
because the corresponding F_A1 port is offline. However, N_2 comes back online. See
on page 45 for the original fail over scenario.
The ports F_1 and F_2 are mapped to N_1 and continue routing to N_3. Ports F_3 and F_4, which
were originally mapped to N_2, are disabled and rerouted to N_2, and then enabled.
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failoverdisable -pg pgid command to disable failover.
--
switch:admin> ag --failoverdisable -pg 3
Failover policy is disabled for port group 3
Downgrading to Fabric OS v6.3.0 or earlier is supported.
Upgrading from v6.3.0 to v6.4.0 or downgrading from v6.4.0 to v6.3.0 will not change failover
settings.
When an N_Port comes back online, with Failback enabled, the F_Ports that were originally
mapped to it are temporarily disabled.
The F_Port is rerouted to the primary mapped N_Port, and then re-enabled.
The host establishes a new connection with the fabric.
Figure 11 on page 49, the Access Gateway N_1 remains disabled
Figure 10
Access Gateway Administrator's Guide
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