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replacement_timeoutcontrols how long the iSCSI layer should wait for a timed-out path/session to reestablish itself before failing any commands on it. The default
replacement_timeoutvalue is 120 seconds.
/etc/iscsi/iscsid.confand edit the following line:
node.session.timeo.replacement_timeout = [replacement_timeout]
1 queue_if_no_pathoption in
/etc/multipath.confsets iSCSI timers to immediately defer commands to the multipath layer (refer to Section 39.2, “iSCSI Settings With
dm-multipath”). This setting prevents I/O errors from propagating to the application; because of this, you can set
replacement_timeoutto 15-20 seconds.
By configuring a lower
replacement_timeout, I/O is quickly sent to a new path and executed (in the event of a NOP-Out timeout) while the iSCSI layer attempts to re-establish the failed path/session. If all paths time out, then the multipath and device mapper layer will internally queue I/O based on the settings in
Whether your considerations are failover speed or security, the recommended value for
replacement_timeoutwill depend on other factors. These factors include the network, target, and system workload. As such, it is recommended that you thoroughly test any new configurations to
replacements_timeoutbefore applying it to a mission-critical system.