[Ocfs2-users] Ocfs2-users Digest, Vol 65, Issue 16

[David Johle]

>Date: Wed, 20 May 2009 13:32:15 -0400
>From: "Charlie Sharkey" <charlie.sharkey at bustech.com>
>Subject: Re: [Ocfs2-users] OCFS2 mount points will not automatically
>         mount   onboot
>To: <ocfs2-users at oss.oracle.com>
>Message-ID:
>         <03FB5D708BE3C8448E8079186A56CDE6011CA77D at BTIBURMAIL.bustech.com>
>Content-Type: text/plain; charset="us-ascii"
>
>
>Check the status of the multipath demon:   multipathd  status
>I have seen a problem where the demon would die after starting. I
>believe there is
>an update to multipath tools to fix this (at lease for Suse there is).
>
>You should be mounting by label rather that /dev/dm-x. Label the drives
>and then
>use: LABEL=mylabel  in the fstab file. The relationship between dm-x and
>any particular
>is not persistent between boots. In other words, dm-2 may be the oragrid
>volume next time.
>
>I have seen another problem.  After mounting by label the 'mount'
>command shows the drives
>mounting as /dev/sdx rather than a multipathed device. You may have to
>delay the multipath
>demon at boot time for things to settle. Adding a 'sleep 5' to the
>appropriate startup script
>will usually fix it.
>
>good luck,
>cs


Adding delays to scripts to "fix" race conditions is generally not a 
good long term solution.

I also don't think the problem here is even a race condition, 
actually.  I had this same issue when setting up persistent mounting 
of multipath volumes by label.  What I found to be the cause for 
/dev/sdX being chosen over a /dev/mapper/* device lies in the 
file:  /etc/blkid/blkid.tab

The order that entries are written to the blkid cache file affects 
the order the devices are chosen when mounting by label.  In 
otherwords, you need to ensure that your multipath device is listed first.


Also, something else you can do instead of filesystem labels, if 
you'd like, is assign the multipath device an alias.  This gives you 
something like /dev/mapper/youralias as a device, and then you base 
your fstab/mount commands on that unchanging name.  See the 
multipathd documentation, look for the alias directive.