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10.4.2 Using LVM2
To make LVM2 recognize the MPIO devices as possible physical volumes, you must
modify /etc/lvm/lvm.conf. It is important to modify it in a way that it does not
scan and use the physical paths, but only accesses the multipath IO storage through the
multipath IO layer. To do so, change the filter and types entry in /etc/lvm/
lvm.conf as follows:
filter = [ "a|/dev/disk/by-name/.*|", "r|.*|" ]
types = [ "device-mapper", 253 ]
This allows LVM2 to scan only the by-name paths and reject everything else. If you
are also using LVM2 on non-multipath IO devices, make the necessary adjustments to
suit your setup.
10.4.3 Using mdadm
The same as for LVM2 applies to mdadm as well—the devices must be accessed by
name rather than by physical path. Therefore the DEVICE entry in /etc/mdadm
.conf must be modified:
DEVICE /dev/disk/by-name/*
10.4.4 Partitions
Currently it is not possible to partition multipath IO devices themselves. If the underlying
physical device is already partitioned, the multipath IO device reflects those partitions
and the layer provides /dev/disk/by-name/>name<p1 ... pN devices so you
can access the partitions through the multipath IO layer.
As a consequence, the devices need to be partitioned prior to enabling multipath IO. If
you change the partitioning in the running system, Multipath IO does not automatically
detect and reflect these changes. It must be reinitialized, which usually requires a reboot.
Multipath IO
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Troubleshooting
