25.21. Configuring Maximum Time for Error Recovery with eh_deadline
eh_deadlineparameter. Using the
eh_deadlineparameter 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_deadlinein 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.
eh_deadlinefunctionality provides no additional benefit, as the I/O and error recovery commands fail immediately, which allows multipath to retry.
eh_deadlineparameter enables you to configure the maximum amount of time that the SCSI error handling mechanism attempts to perform error recovery before stopping and resetting the entire HBA.
eh_deadlineis specified in seconds. The default setting is
off, which disables the time limit and allows all of the error recovery to take place. In addition to using
sysfs, a default value can be set for all SCSI HBAs by using the
eh_deadlineexpires, the HBA is reset, which affects all target paths on that HBA, not only the failing one. As a consequence, I/O errors can occur if some of the redundant paths are not available for other reasons. Enable
eh_deadlineonly if you have a fully redundant multipath configuration on all targets.