Setup Guide

Fast I/O Failure for Fibre Channel Devices
This topic describes the Fast I/O Failure feature for FC devices and details the setting recommendations.
AIX supports Fast I/O Failure for Fibre Channel devices after link events in a switched environment.
When the FC adapter driver detects a link event, such as a lost link between a storage device and a switch, it waits for the
fabric to stabilize (approximately 15 s). If the device is not on the fabric, the FC adapter driver fails all new I/Os or future retries
of the failed I/Os, until the device rejoins the fabric. The fscsi device attribute fc_err_recov controls Fast I/O Failure
(default value is delayed_fail).
It is recommended to enable Fast I/O Failure for FC adapters that are connected to PowerStore storage.
To enable Fast I/O Failure for all fscsi devices, set the fc_err_recov attribute to fast_fail, as shown in the following
example:
NOTE: In the example, the fscsi device instance is fscsi0.
chdev -l fscsi0 -a fc_err_recov=fast_fail -P
Run the following command to verify that the setting was enabled in the ODM:
lsattr -El fscsi0
NOTE: The -P flag only modifies the setting in the ODM and requires a system reboot for the changes to apply.
Fast fail logic is applied when the switch sends a Registered State Change Notification (RSCN) to the adapter driver, indicating
a link event with a remote storage device port.
Fast I/O Failure is useful when multipathing software is used. Setting the fc_err_recov attribute to fast_fail can
decrease I/O failure due to link loss between the storage device and switch, by supporting faster failover to alternate paths.
Dynamic Tracking
This topic describes the dynamic tracking logic for FC devices and details the setting recommendations.
Dynamic tracking logic is applied when the adapter driver receives an indication from the switch that a link event with a remote
storage device port has occurred.
If dynamic tracking of FC devices is enabled, the FC adapter driver detects when the Fibre Channel N_Port ID of a device
changes. The FC adapter driver then reroutes the traffic that is destined for that device to the new address, while the devices
are still online.
Events that can cause an N_Port ID to change include:
● Moving a cable that connects a switch to a storage device from one switch port to another.
● Connecting two separate switches using an Inter-Switch Link (ISL).
● Rebooting a switch.
The fscsi device attribute dyntrk controls dynamic tracking of FC devices (default value is no for non-NPIV configurations).
It is recommended to enable dynamic tracking for PowerStore volumes.
To enable dynamic tracking for FC devices, change all fscsi device attributes to dyntrk=yes, as shown in the following
example:
NOTE: In the example, the fscsi device instance is fscsi0.
chdev -l fscsi0 -a dyntrk=yes -P
Run the following command to verify that the setting was enabled in the ODM:
lsattr -El fscsi0
NOTE: The -P flag only modifies the setting in the ODM and requires a system reboot for the changes to apply.
Host Configuration for AIX 41