Novell LINUX ENTERPRISE SERVER 11 - STORAGE ADMINISTRATION GUIDE 2-23-2010, Administration Manual, Page: 46 / 140

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7.2.3 Using LVM2 on Multipath Devices
By default, LVM2 does not recognize multipathed devices. To make LVM2 recognize the
multipathed devices as possible physical volumes, you must modify
/etc/lvm/lvm.conf
. It is
important to modify it so that it does not scan and use the physical paths, but only accesses the
multipath I/O storage through the multipath I/O layer. If you are using user-friendly names, make
sure to specify the path so that it cans only the device mapper names for the device (
/dev/disk/by-
id/dm-uuid-.*-mpath-.*
) after multipathing is configured.
To modify
/etc/lvm/lvm.conf
for multipath use:
1 Open the
/etc/lvm/lvm.conf
file in a text editor.
2 Change the
filter
and
types
entry in
/etc/lvm/lvm.conf
as follows:
filter = [ "a|/dev/disk/by-id/.*|", "r|.*|" ]
This allows LVM2 to scan only the by-id paths and reject everything else.
If you are using user-friendly names, specify the path as follows so that only the device mapper
names are scanned after multipathing is configured:
filter = [ "a|/dev/disk/by-id/dm-uuid-.*-mpath-.*|", "r|.*|" ]
3 If you are also using LVM2 on non-multipathed devices, make the necessary adjustments to
suit your setup.
filter = [ "a|/dev/disk/by-id/.*|", "r|.*|" ]
4 Save the file.
5
Add dm-multipath to
/etc/sysconfig/kernel:INITRD_MODULES
.
6 Make a new
initrd
to ensure that the Device Mapper Multipath services are loaded with the
changed settings. Enter
mkinitrd -f multipath
7
Reboot the server to apply the changes.
7.2.4 Using mdadm with Multipath Devices
The
mdadm
tool requires that the devices be accessed by the ID rather than by the device node path.
Therefore, the
DEVICE
entry in
/etc/mdadm.conf
should be set as follows:
DEVICE /dev/disk/by-id/*
If you are using user-friendly names, specify the path as follows so that only the device mapper
names are scanned after multipathing is configured:
DEVICE /dev/disk/by-id/dm-uuid-.*-mpath-.*
7.2.5 Using --noflush with Multipath Devices
The option --noflush should always be used when running on multipath devices.
For example, in scripts where you perform a table reload, you use the --noflush option on resume to
ensure that any outstanding I/O is not flushed, because you need the multipath topology information.
load
resume --noflush