Chapter 7. Using Fibre Channel devices
RHEL 8 provides the following native Fibre Channel drivers:
7.1. Resizing Fibre Channel Logical Units
As a system administrator, you can resize Fibre Channel logical units.
To determine which devices are paths for a
To re-scan Fibre Channel logical units on a system that uses multipathing:
$ echo 1 > /sys/block/sdX/device/rescan
7.3. Fibre Channel configuration files
Following is the list of configuration files in the
/sys/class/ directory that provide the user-space API to Fibre Channel.
The items use the following variables:
- Host number
- Bus number
- Logical unit (LUNs)
- Remote port number
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 configuration in
- 24-bit port ID/address
- 64-bit node name
- 64-bit port name
Remote port configuration in
Controls when the scsi device gets removed from the system. After
dev_loss_tmotriggers, the scsi device is removed. In the
multipath.conffile , you can set
In Red Hat Enterprise Linux 8, if you do not set the
dev_loss_tmois capped to
600seconds. By default,
fast_io_fail_tmois set to
5seconds in Red Hat Enterprise Linux 8 if the
multipathdservice is running; otherwise, it is set to
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.
fast_io_fail_tmois set to any value except off,
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
Host configuration in
Instructs the driver to rediscover remote ports.
7.4. DM Multipath overrides of the device timeout
sysfs option controls the timeout for a particular iSCSI device. The following options globally override
replacement_timeoutconfiguration option globally overrides the
recovery_tmovalue for all iSCSI devices.
For all iSCSI devices that are managed by DM Multipath, the
fast_io_fail_tmooption in DM Multipath globally overrides the
fast_io_fail_tmooption in DM Multipath also overrides the
fast_io_fail_tmooption in Fibre Channel devices.
The DM Multipath
fast_io_fail_tmo option takes precedence over
replacement_timeout. Red Hat does not recommend using
replacement_timeout to override
recovery_tmo in devices managed by DM Multipath because DM Multipath always resets
recovery_tmo when the
multipathd service reloads.