25.22. Configuring Maximum Time for Error Recovery with eh_deadline

In most scenarios, you do not need to enable the eh_deadline parameter. Using the eh_deadline parameter can be useful in certain specific scenarios, for example if a link loss occurs between a Fibre Channel switch and a target port, and the Host Bus Adapter (HBA) does not receive Registered State Change Notifications (RSCNs). In such a case, I/O requests and error recovery commands all time out rather than encounter an error. Setting eh_deadline in this environment puts an upper limit on the recovery time, which enables the failed I/O to be retried on another available path by multipath.

However, if RSCNs are enabled, the HBA does not register the link becoming unavailable, or both, the eh_deadline functionality provides no additional benefit, as the I/O and error recovery commands fail immediately, which allows multipath to retry.