8.2. Determining the link loss behavior of device using Fibre Channel

Procedure

• Determine the state of a remote port:

  $ cat /sys/class/fc_remote_ports/rport-host:bus:remote-port/port_state

  This command returns one of the following output:

  • Blocked when the remote port along with devices accessed through it are blocked.

  • Online if the remote port is operating normally

    If the problem is not resolved within dev_loss_tmo seconds, the rport and devices will be unblocked. All I/O running on that device along with any new I/O sent to that device will fail.

    When a link loss exceeds dev_loss_tmo, the scsi_device and sd_N_ devices are removed. Typically, the Fibre Channel class does not alter the device, for example, /dev/sda remains /dev/sda. This is because the target binding is saved by the Fibre Channel driver and when the target port returns, the SCSI addresses are recreated faithfully. However, this cannot be guaranteed, the device will be restored only if no additional change on in-storage box configuration of LUNs is made.