Below is a introduction of Fibre Channel API in userspace on Linux(RHEL,CentOS,SL)
Below is a list of /sys/class/ directories that contain files used to provide the userspace API. In each item:

H -- host numbers are designated

B -- bus numbers

T -- targets 

L -- logical unit numbers (LUNs)

R -- and remote port numbers
If your system is using multipath software, Red Hat recommends that you consult your hardware vendor before changing any of the values described in this section.

Transport : /sys/class/fc_transport/targetH: B: T/
port_id — 24-bit port ID /address
node_name — 64-bit node name
port_name — 64-bit port name
Remoteport : /sys/class/fc_remote_ports/rport-H: B-R/
dev_loss_tmo — number of seconds to wait before marking a link as " bad". Once a link is marked bad, I/O running on its corresponding path (along with any new I/O on that path) will be failed. The default dev_loss_tmo value varies, depending on which driver/device is used. If a Qlogic adapter is used, the default is 35 seconds, while if an Emulex adapter is used, it is 30 seconds. The dev_loss_tmo value can be changed via the scsi _transport_fc module parameter dev_loss_tmo , although the driver can override this timeout value.
The maximum dev_loss_tmo value is 600 seconds. If dev_loss_tmo is set to zero or any value greater than 600, the driver's internal timeouts will be used instead.
fast_io_fail_tmo — length of time to wait before failing I/O executed when a link problem is detected. I/O that reaches the driver will fail. If I/O is in a blocked queue, it will not be failed until dev_loss_tmo expires and the queue is unblocked.
Host : /sys/class/fc_host/hostH/
issue_lip — instructs the driver to rediscover remote ports.


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