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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 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/addressnode_name— 64-bit node nameport_name— 64-bit port name
- Remote Port:
/sys/class/fc_remote_ports/rport-H:B-R/ port_idnode_nameport_namedev_loss_tmo: controls when the scsi device gets removed from the system. Afterdev_loss_tmotriggers, the scsi device is removed.Inmultipath.conf, you can setdev_loss_tmotoinfinity, which sets its value to 2,147,483,647 seconds, or 68 years, and is the maximumdev_loss_tmovalue.In Red Hat Enterprise Linux 7, if you do not set thefast_io_fail_tmooption,dev_loss_tmois capped to 600 seconds. By default,fast_io_fail_tmois set to 5 seconds in Red Hat Enterprise Linux 7 if themultipathdservice is running; otherwise, it is set tooff.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 untildev_loss_tmoexpires and the queue is unblocked.Iffast_io_fail_tmois set to any value exceptoff,dev_loss_tmois uncapped. Iffast_io_fail_tmois set tooff, no I/O fails until the device is removed from the system. Iffast_io_fail_tmois set to a number, I/O fails immediately when thefast_io_fail_tmotimeout triggers.
- Host:
/sys/class/fc_host/hostH/ port_idissue_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:
lpfcqla2xxxzfcpbfa
Important
The qla2xxx driver runs in initiator mode by default. To use qla2xxx with Linux-IO, enable Fibre Channel target mode with the corresponding
qlini_mode module parameter.
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.conf qla2xxx module configuration file:
options qla2xxx qlini_mode=disabled
Then, use the
dracut -f command 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.
lpfc | qla2xxx | zfcp | bfa | |
|---|---|---|---|---|
Transport port_id | X | X | X | X |
Transport node_name | X | X | X | X |
Transport port_name | X | X | X | X |
Remote Port dev_loss_tmo | X | X | X | X |
Remote Port fast_io_fail_tmo | X | X [a] | X [b] | X |
Host port_id | X | X | X | X |
Host issue_lip | X | X | X | |
[a]
Supported as of Red Hat Enterprise Linux 5.4
[b]
Supported as of Red Hat Enterprise Linux 6.0
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