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5.5. Issues with Large Number of LUNs

When a large number of LUNs are added to a node, using multipathed devices can significantly increase the time it takes for the udev device manager to create device nodes for them. If you experience this problem, you can correct it by deleting the following line in /etc/udev/rules.d/40-multipath.rules:
KERNEL!="dm-[0-9]*", ACTION=="add", PROGRAM=="/bin/bash -c '/sbin/lsmod | /bin/grep ^dm_multipath'", RUN+="/sbin/multipath -v0 %M:%m"
This line causes the udev device manager to run multipath every time a block device is added to the node. Even with this line removed, the multipathd daemon will still automatically create multipathed devices, and multipath will still be called during the boot process for nodes with multipathed root file systems. The only change is that multipathed devices will not be automatically created when the multipathd daemon is not running, which should not be a problem for the vast majority of multipath users.