Labeling Multipath drives

[Jeffrey O'brien]

>>> 
From: 	Kenny Lussier <klussier at gmail.com>
To:	mark <prgrmr at gmail.com>
CC:	<gnhlug-discuss at gnhlug.org>
Date: 	3/18/2009 9:40 AM
Subject: 	Re: Labeling Multipath drives

This is true. For example, in /dev/mapper there is a device called 350002ac00092072a1. I can label the device, but that also creates labels on what the OS sees as /dev/sdc, /dev/sdd, /dev/sde, /dev/sdf, /dev/sdg, /dev/sdh, /dev/sdi, and /dev/sdj, so a mount fails. The SAN doesn't come with client-side multipathing software. That is really up to the OS vendor. In this case, I am using device-mapper-multipath on RHEL5.3AP (w/ their clustering suite) with a 3Par SAN. The SAN is presenting all of the paths to both systems simultaneously. That isn't a problem. And, if I wanted to use GFS to have the disk mounted to both servers simultaneously, then that would work just fine. But, I can't have the disk mounted on more then one system at any given time. 


>>>

http://www.scribd.com/doc/2673197/Using-DeviceMapper-Multipath-Configuration-and-Administration-for-Red-Hat-Enterprise-Linux-51 

Here is a redhat doc on 5.1, it should be relevant still.  You have to reference and format the mpath device instead of the individual device.  Also make sure the dm-multipath kernel module is loaded and the daemons are running.  Do you have the /etc/multipath.conf configured?

Cheers,
Jeff

/3/18 mark <prgrmr at gmail.com>

> 2009/3/18 Kenny Lussier <klussier at gmail.com>
>
> Hi All,
>>
>>
>> I currently have a failover cluster  with a shared  iSCSI disk. It is just
>> an ext3 partition that has a disk label. If the primary box drops, the
>> backup box (through the magic of clustering), knows that it needs to mount
>> the disk where "LABEL=HA_DISK". However, I am soon going to be moving the
>> storage to a fiber channel SAN. The boxes will each have two FC HBA's in
>> them, giving them each eight total paths to the SAN volume. The problem that
>> I have is that if I use e2label on the partition that ends up in
>> /dev/mapper, I can't mount by label. I get an error saying "Multiple drives
>> found with identical label". Does anyone know how to work around this?
>>
>> TIA,
>> Kenny
>>
>
> Your SAN should have multi-pathing software that presents the paths on each
> box as a single virtual device to the OS.  The SAN should also be cluster
> aware and present all the paths to the disk to both systems
> simultaneously.   What OS, brand of SAN and clustering software are you
> using?
>

This is true. For example, in /dev/mapper there is a device called
350002ac00092072a1.  I can label the device, but that also creates labels on
what the OS sees as /dev/sdc, /dev/sdd, /dev/sde, /dev/sdf, /dev/sdg,
/dev/sdh, /dev/sdi, and /dev/sdj, so a mount fails.  The SAN doesn't come
with client-side multipathing software. That is really up to the OS vendor.
In this case, I am using device-mapper-multipath on RHEL5.3AP (w/ their
clustering suite) with a 3Par SAN. The SAN is presenting all of the paths to
both systems simultaneously. That isn't a problem. And, if I wanted to use
GFS to have the disk mounted to both servers simultaneously, then that would
work just fine. But, I can't have the disk mounted on more then one system
at any given time.


Thanks,
Kenny