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10.3.5 Managing IO in Error Situations
In certain scenarios where the driver, the host bus adapter, or the fabric experiences
errors leading to loss of all paths, all IO should be queued instead of being propagated
upwards.
This can be achieved with the following setting in /etc/multipath.conf.
defaults {
default_features "1 queue_if_no_path"
}
Because this leads to IO being queued forever unless a path is reinstated, make sure
that multipathd is running and works for your scenario. Otherwise, IO might be stalled
forever on the affected MPIO device until reboot or until you manually issue
dmsetup message <NAME> 0 fail_if_no_path
This immediately cause all queued IO to fail (replace <NAME> with the the correct
map name). You can reactivate queueing by issuing the following command:
dmsetup message <NAME> 0 queue_if_no_path
You can also use these two commands to switch between modes for testing before
committing the command to /etc/multipath.conf.
10.4 Using the Devices
MPIO devices can be used directly, with LVM, and with mdadm.
10.4.1 Using the Devices Directly
If you want to use the entire LUNs directly (for example, if you are using the SAN
features to partition your storage), you can simply use the /dev/disk/by-name/
xxx names directly for mkfs, fstab, your application, etc.
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Installation and Administration
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Troubleshooting
