# man multipath.conf
fast_io_fail_tmo
Specify the number of seconds the scsi layer will wait after a problem has been detected on a FC remote port before failing IO to devices on that remote port. This should be smaller than dev_loss_tmo. Setting this to off will disable the timeout.
dev_loss_tmo
Specify the number of seconds the scsi layer will wait after a problem has been detected on a FC remote port before removing it from the system. This can be set to "infinity" which sets it to the max value of 2147483647 seconds, or 68 years.
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Regarding fail_if_no_path, please check:
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https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/DM_Multipath/queueifnopath_issues.html
5.4. Issues with queue_if_no_path feature
If features "1 queue_if_no_path" is specified in the /etc/multipath.conf file, then any process that issues I/O will hang until one or more paths are restored. To avoid this, set the no_path_retry N parameter in the /etc/multipath.conf file (where N is the number of times the system should retry a path).
When you set the no_path_retry parameter, remove the features "1 queue_if_no_path" option from the /etc/multipath.conf file as well. If, however, you are using a multipathed device for which the features "1 queue_if_no_path" option is set as a compiled-in default, as it is for many SAN devices, you must explicitly add features "0" to override this default. You can do this by copying the existing devices section for your device from /usr/share/doc/device-mapper-multipath-0.4.7/multipath.conf.defaults into /etc/multipath.conf and editing it to suit your needs.
If you need to use the features "1 queue_if_no_path" option and you experience the issue noted here, use the dmsetup command to edit the policy at runtime for a particular LUN (that is, for which all the paths are unavailable). For example, if you want to change the policy on the multipath device mpath2 from "queue_if_no_path" to "fail_if_no_path", execute the following command.
dmsetup message mpath2 0 "fail_if_no_path"
Note that you must specify the mpathn alias rather than the path.
fast_io_fail_tmo
Specify the number of seconds the scsi layer will wait after a problem has been detected on a FC remote port before failing IO to devices on that remote port. This should be smaller than dev_loss_tmo. Setting this to off will disable the timeout.
dev_loss_tmo
Specify the number of seconds the scsi layer will wait after a problem has been detected on a FC remote port before removing it from the system. This can be set to "infinity" which sets it to the max value of 2147483647 seconds, or 68 years.
----------------
Regarding fail_if_no_path, please check:
----------------
https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/DM_Multipath/queueifnopath_issues.html
5.4. Issues with queue_if_no_path feature
If features "1 queue_if_no_path" is specified in the /etc/multipath.conf file, then any process that issues I/O will hang until one or more paths are restored. To avoid this, set the no_path_retry N parameter in the /etc/multipath.conf file (where N is the number of times the system should retry a path).
When you set the no_path_retry parameter, remove the features "1 queue_if_no_path" option from the /etc/multipath.conf file as well. If, however, you are using a multipathed device for which the features "1 queue_if_no_path" option is set as a compiled-in default, as it is for many SAN devices, you must explicitly add features "0" to override this default. You can do this by copying the existing devices section for your device from /usr/share/doc/device-mapper-multipath-0.4.7/multipath.conf.defaults into /etc/multipath.conf and editing it to suit your needs.
If you need to use the features "1 queue_if_no_path" option and you experience the issue noted here, use the dmsetup command to edit the policy at runtime for a particular LUN (that is, for which all the paths are unavailable). For example, if you want to change the policy on the multipath device mpath2 from "queue_if_no_path" to "fail_if_no_path", execute the following command.
dmsetup message mpath2 0 "fail_if_no_path"
Note that you must specify the mpathn alias rather than the path.
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