[dm-devel] Configuring multipath for root device

[Hannes Reinecke]

Chandra Seetharaman wrote:
> I am working on a multipath usage document. Attached is the installation
> section of that document.
> 
> Note that it is written for RHEL5 U1 and SLES10 SP1.
> 
> Good Luck,
> 
> chandra
> 
> On Wed, 2007-12-19 at 13:02 -0800, Pradipmaya Maharana wrote:
>> Hi All,
>>
>> Is there a process/document that talks about how to configure
>> root/boot device for multipath?
>>
>> Thanks and Regards,
>> Pradipmaya.
>>
>> --
>> dm-devel mailing list
>> dm-devel at redhat.com
>> https://www.redhat.com/mailman/listinfo/dm-devel
>>
>> ------------------------------------------------------------------------
>>
>> 4.1. Installation instructions for SLES10
>>
>> Note: This is tested on SLES10 SP1. If you have any other version, your
>> mileage may vary.
>>
>>    1. Install the OS in a device that has multiple paths. Make sure the
>> root device's "Mount by" option is set to "Device by-id" (this option is
>> available under "expert partitioner" as "fstab options").
>>    2. Complete the installation. Let the system boot up in multiuser mode.
>> Make sure the root device, swap device are all referenced by their by-id
>> device node entries instead of /dev/sd* type names. If they are not, fix
>> them first.
>>    3. Once booted, update /etc/multipath.conf If you have to make changes
>> to /etc/multipath.conf, make the changes.
>>       Note: the option "user_friendly_names" is not supported by initrd.
>> So, if you have user_friendly_names in your /etc/multipath.conf file,
>> comment it for now, you can uncomment it later.
>>    4. Enable multipathing by running the following commands
>>           * chkconfig boot.multipath on
>>
>>           * chkconfig multipathd on 
>>    5. Add multipath module to initrd
>>
>>       Edit the file /etc/sysconfig/kernel and add "dm-multipath" to
>> INITRD_MODULES". Note: If your storage devices needs a hardware handler,
>> add the corresponding module to INITRD_MODULES, in addition to
>> "dm-multipath". For example add "dm-rdac" and "dm-multipath" to support
>> IBM's DS4K storage devices
>>    6.  Run mkinitrd
>>       Note: You can uncomment the user friendly name if you have commented it above.
>>    7. Reboot 
>>
>> The system will come up with the root disk on a multipathed device.
>>
>> Note: You can switch off multipathing to the root device by adding
>> multipath=off to the kernel command line.
>>
ACK. This is the correct way.

Thanks for writing this up.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
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