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Chapter 26. Fibre Channel

This section discusses the Fibre Channel API, native Red Hat Enterprise Linux 6 Fibre Channel drivers, and the Fibre Channel capabilities of these drivers.

26.1. Fibre Channel API

Following is a list of /sys/class/ directories that contain files used to provide the userspace API. In each item, host numbers are designated by H, bus numbers are B, targets are T, logical unit numbers (LUNs) are L, and remote port numbers are R.

Important

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
Remote Port: /sys/class/fc_remote_ports/rport-H:B-R/
  • port_id
  • node_name
  • port_name
  • dev_loss_tmo: controls when the scsi device gets removed from the system. After dev_loss_tmo triggers, the scsi device is removed.
    In multipath.conf, you can set dev_loss_tmo to infinity, which sets its value to 2,147,483,647 seconds, or 68 years, and is the maximum dev_loss_tmo value.
    In Red Hat Enterprise Linux 6, fast_io_fail_tmo is not set by default, hence dev_loss_tmo value is capped to 600 seconds.
  • fast_io_fail_tmo: specifies the number of seconds to wait before it marks a link as "bad". Once a link is marked bad, existing running I/O or any new I/O on its corresponding path fails.
    If I/O is in a blocked queue, it will not be failed until dev_loss_tmo expires and the queue is unblocked.
    If fast_io_fail_tmo is set to any value except off, dev_loss_tmo is uncapped. If fast_io_fail_tmo is set to off, no I/O fails until the device is removed from the system. If fast_io_fail_tmo is set to a number, I/O fails immediately when fast_io_fail_tmo triggers.
Host: /sys/class/fc_host/hostH/
  • port_id
  • issue_lip: instructs the driver to rediscover remote ports.