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25.4. Fibre Channel
This section discusses the Fibre Channel API, native Red Hat Enterprise Linux 7 Fibre Channel drivers, and the Fibre Channel capabilities of these drivers.
25.4.1. 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
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.
port_id— 24-bit port ID/address
node_name— 64-bit node name
port_name— 64-bit port name
- Remote Port:
dev_loss_tmo: controls when the scsi device gets removed from the system. After
dev_loss_tmotriggers, the scsi device is removed.In
multipath.conf, you can set
infinity, which sets its value to 2,147,483,647 seconds, or 68 years, and is the maximum
dev_loss_tmovalue.In Red Hat Enterprise Linux 7, if you do not set the
dev_loss_tmois capped to 600 seconds. By default,
fast_io_fail_tmois set to 5 seconds in Red Hat Enterprise Linux 7 if the
multipathdservice is running; otherwise, it is set to
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_tmoexpires and the queue is unblocked.If
fast_io_fail_tmois set to any value except
dev_loss_tmois uncapped. If
fast_io_fail_tmois set to
off, no I/O fails until the device is removed from the system. If
fast_io_fail_tmois set to a number, I/O fails immediately when the
issue_lip: instructs the driver to rediscover remote ports.
25.4.2. Native Fibre Channel Drivers and Capabilities
Red Hat Enterprise Linux 7 ships with the following native Fibre Channel drivers:
The qla2xxx driver runs in initiator mode by default. To use qla2xxx with Linux-IO, enable Fibre Channel target mode with the corresponding
First, make sure that the firmware package for your qla device, such as ql2200-firmware or similar, is installed.
To enable target mode, add the following parameter to the
/usr/lib/modprobe.d/qla2xxx.confqla2xxx module configuration file:
options qla2xxx qlini_mode=disabled
Then, use the
dracut -fcommand to rebuild the initial ramdisk (
initrd), and reboot the system for the changes to take effect.
Table 25.1, “Fibre Channel API Capabilities” describes the different Fibre Channel API capabilities of each native Red Hat Enterprise Linux 7 driver. X denotes support for the capability.
Table 25.1. Fibre Channel API Capabilities