Before you configure the Linux® operating system
for a host that attaches to the system, ensure that the correct Device Mapper Multipath Tool
(DMMP) is installed and configured correctly for the Linux
hosts that use DMMP as a multipath driver. Currently, Red Hat Enterprise Linux 5 and later and SUSE Linux
Enterprise Server 11 support DMMP as a multipath driver and include it on a distribution disk.
Procedure
-
Ensure that the DMMP packages are installed on your Linux host.
-
In the DMMP configuration file, /etc/multipath.conf, ensure that the
default settings have the values that are described in Settings for Linux hosts.
Note: Linux usually enables
multipathing automatically.
However, in some cases such as the RH 6.3
SAN boot installation, the multipathing is not configured properly. If this situation occurs, you must manually
edit the
/etc/multipath.conf file. For information about DM-multipath,
see the Linux
Storage Administration Guide or
DM-Multipathing Installation and
Configuration Guide for your kernel from the Linux provider. For more information about Linux system configuration, see the following website:
http://www.ibm.com/support/knowledgecenter/linuxonibm/liaab/ic-homepage.htm
Note: If you are using RHEL6 or SUSE Linux Enterprise
Server 11 Service Pack 2, use prio "alua"
instead of prio_callout
"/sbin/mpath_prio_alua /dev/%n"
to disable the Using deprecated
prio_callout
message. This value disables only the error message and does not affect
operations. If prio_callout "/sbin/mpath_prio_alua /dev/%n" is set on
SUSE Linux Enterprise Server 11 Service Pack 2, the
Using deprecated prio_callout
message is issued for all devices when the
multipath command is used.
-
To enable DMMP autoload during an operating system boot, issue the following commands as
root:
- For Red Hat Enterprise Linux 5 or later, issue one
of the following commands.
- For SUSE Linux Enterprise Server 11, issue one of
the following commands.
After you run one of these commands, issue one of the following commands.
-
Start DMMP manually by completing the following steps.
- Optional:
If you are using SUSE Linux Enterprise Server, run the
/etc/init.d/boot.multipath start command before you start the DMMP.
-
Start DMMP daemon by issuing the /etc/init.d/multipathd start command:
.
-
Run the commands multipath or multipath -v2 to scan the
multipath devices.
-
Issue the multipath -ll command to view the detailed information of the
multipath devices. The command has the following output:
mpath1 (36005076801860022900000000000019a) IBM,2145
[size=2.0G][features=0][hwhandler=0]
\_ round-robin 0 [prio=200][ enabled]
\_ 4:0:0:1 sdd 8:48 [active][ready]
\_ 5:0:0:1 sdt 65:48 [active][ready]
\_ round-robin 0 [prio=40][ active]
\_ 4:0:2:1 sdak 66:64 [active][ready]
\_ 5:0:2:1 sdal 66:80 [active][ready]
Results
Note: If the new device cannot be found after you issue the multipath
command, you must reload the HBA driver or reboot the server, and reissue the
multipath command after Linux
recognizes the new device in the SCSI layer with a name like sd*. The HBA driver must recognize
the new devices before DMMP can recognize them and manage them. To view the detailed status of
the multipath devices, issue the multipath -ll command.