The valid path statuses are:
Path is down and you shouldn't try to send commands to it.
Path is up and I/O can be sent to it.
Only emc_clariion checker when path not available for "normal" operations.
Only hp_sw and rdac checkers. Indicates a "passive/standby" path on active/passive HP arrays. These paths will return valid answers to certain SCSI commands (tur, read_capacity, inquiry, start_stop), but will fail I/O commands. The path needs an initialization command to be sent to it in order for I/Os to succeed.
Available for all async checkers when a check IO is in flight.
Only tur checker when command timed out.
If a path fails after being up for less than delay_watch_checks checks, when it comes back up again, it will not be marked as up until it has been up for delay_wait_checks checks. During this time, it is marked as "delayed".