HP 3PAR SUSE Linux Enterprise Implementation Guide

NOTE: When considering the use of the Device-mapper user_friendly_names, be

aware of the following - Using the user_friendly_names option can be problematic in

the following situations: w Root Device Is Using Multipath: If the system root device is using

multipath and you use the user_friendly_names option, the user-friendly settings in the

/var/lib/multipath/bindings file are included in the initrd. If you later change the

storage setup, such as by adding or removing devices, there is a mismatch between the

bindings setting inside the initrd and the bindings settings in /var/lib/multipath/

bindings.

7. Verify that /etc/fstab and /boot/grub/menu.1st are using /dev/disk/by-id. The

following example shows the created and exported root volume with its ID in these two files.

createvv host.volume [...]

createvlun host.volume 0 sles

showvlun -lvw

0 sles boot.volume 50002AC00003011b

ls -l /dev/disk/by-id*

[...] scsi-350002ac00003011b -> ../../sda

[...] scsi-350002ac00003011b-part1 -> ../../sdd1

cat /etc/fstab

/dev/disk/by-id/scsi-350002ac00003011b-part1 swap swap defaults 0 0

/dev/disk/by-id/scsi-350002ac00003011b-part2 / ext3 acl,user_xattr 1 1

[...]

cat /boot/grub/menu.1st

[...]

root=/dev/disk/by-id/scsi-350002ac00003011b-part2

resume=/dev/disk/by-id/scsi-350002ac00003011b-part1

WARNING! A bindings mismatch between initrd and /var/lib/multipath/bindings

can lead to a wrong assignment of mount points to devices, which can result in file system

corruption and data loss. To avoid this problem, we recommend that you use the default

WWID settings for the system root device. You can also use the alias option to override the

user_friendly_names option for the system root device in the /etc/multipath.conf

file.

Configuring Device-mapper Multipathing

The /etc/multipath.conf file is used by Device-mapper where the multipathing parameters

have been set. The default installed /etc/multipath.conf file must be edited with the following

changes for a minimum configuration connecting to an HP 3PAR StoreServ Storage array. Entries

listed in multipath.conf override the default kernel parameters for dm-multipath. In general,

the kernel defaults are sufficient with the exception of the devices entries for HP 3PAR.

1. Remove or comment out all entries in the /etc/multipath.conf file except for the devices

files of devices currently in use.

Configuring Device-mapper Multipathing 67