Novell LINUX ENTERPRISE SERVER 10 SP3 - ARCHITECTURE-SPECIFIC, Administration Manual

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68 SLES 10 SP3: Storage Administration Guide
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To enable multipathing on the existing root device:
1 Install Linux with only a single path active, preferably one where the
by-id
symlinks are listed
in the partitioner.
2 Mount the devices by using the
/dev/disk/by-id
path used during the install.
3
After installation, add
dm-multipath
to
/etc/sysconfig/kernel:INITRD_MODULES
.
4 For System Z, before running mkinitrd, edit the
/etc/zipl.conf
file to change the by-path
information in
zipl.conf
with the same by-id information that was used in the /
etc/fstab
.
5 Re-run
/sbin/mkinitrd
to update the
initrd
image.
6 For System Z, after running mkinitrd, run
zipl
.
7 Reboot the server.
To disable multipathing on the root device:
1 Add
multipath=off
to the kernel command line.
This affects only the root device. All other devices are not affected.
5.9 Configuring Multipath I/O for an Existing
Software RAID
Ideally, you should configure multipathing for devices before you use them as components of a
software RAID device. If you add multipathing after creating any software RAID devices, the DM-
MP service might be starting after the
multipath
service on reboot, which makes multipathing
appear not to be available for RAIDs. You can use the procedure in this section to get multipathing
running for a previously existing software RAID.
For example, you might need to configure multipathing for devices in a software RAID under the
following circumstances:
Š If you create a new software RAID as part of the Partitioning settings during a new install or
upgrade.
Š
If you did not configure the devices for multipathing before using them in the software RAID
as a member device or spare.
Š
If you grow your system by adding new HBA adapters to the server or expanding the storage
subsystem in your SAN.
NOTE: The following instructions assume the software RAID device is
/dev/mapper/mpath0
,
which is its device name as recognized by the kernel. Make sure to modify the instructions for the
device name of your software RAID.
1 Open a terminal console, then log in as the
root
user or equivalent.
Except where otherwise directed, use this console to enter the commands in the following
steps.
2 If any software RAID devices are currently mounted or running, enter the following commands
for each device to dismount the device and stop it.
umount /dev/mapper/mpath0
mdadm --misc --stop /dev/mapper/mpath0