[Linux-cluster] Quorum disk over RAID software device

Thomas Meller thomas.meller at gmx.net
Fri Feb 5 14:56:24 UTC 2010

Many thanks, Gordan.

This could nearly be the solution.
But as I understand, it's not possible to mirror the root-(g)fs to another computing center despite for relying on a new SPOF (if at all possible) or on hardware-dependent solutions.

We had storage problems in the past and could survive them. That's not possible any more, or else we will be bound to a new dependency on a working network infrastructure.

Hmm... our current setup addressed this with half the effort.

Anyway, does anyone in this forum use this technique and can send me the 'init'-script from the initrd?

Thanks again,

-------- Original-Nachricht --------
> Datum: Thu, 04 Feb 2010 18:59:52 +0000
> Von: Gordan Bobic <gordan at bobich.net>
> An: linux clustering <linux-cluster at redhat.com>
> Betreff: Re: [Linux-cluster] Quorum disk over RAID software device

> Thomas,
> It sounds like what you're looking for is Open Shared Root:
> http://www.open-sharedroot.org/
> Gordan
> Thomas Meller wrote:
> > Just found this thread while searching for illumination.
> > 
> > We are running a self-constructed cluster setup since 4 Years on a 2.4
> kernel (RHAS3).
> > It's a two-machine setup, nothing fancy.
> > The fancy thing is that we boot the nodes in different computing centers
> from mirrored SAN devices which are run in separate storage controllers
> located in different computing centers over twice redundant FC fabrics, set
> up a mirrored root fs on these and don't need the local disks except for
> installation.
> > In short: we survived everything.
> > :-)
> > 
> > Up to now, we used a vendor-specific multipath software (RDAC), which I
> want to get rid of. Today we could use RH5.3's dm-multipathing instead.
> > Quorum is done by usage of Robin Miller's excellent scu utility and some
> scripting.
> > 
> > To get there, I need to create an initrd which contains:
> > - the newest qla-drivers
> > - Qlogic's 'scli' utility
> > - multipaths set up to create the raid-mirrors on
> > - mdadm
> > 
> > I am no RedHat-guru and not used to using mkinitrd.
> > The Qlogic installer creates initrds automatically, but not usable for
> me.
> > The mkinird script seems to know md-multipath, but no dm-multipath (as
> far as I understood it's code).
> > 
> > Currently I am on the local disk, have multipath running, made the
> qla-drivers and copied scli, mdadm and the needed libraries manually to the
> initrd.
> > 
> > What do I need in the initrd? I read something of a dm-multipathd.
> > How can I include all modules needed (which?) by running mkinitrd? (do I
> need to have multipath and mirrors already running? Are there configfiles
> to write?)
> > Is it possible to include specified tools (not modules) in a mkinitrd
> run?
> > Why does mdadm -A tell me 'device or ressource busy' on the second of
> two raid1-devices?
> > 
> > You see, I need the big picture as well as a short intro to mkinitrd and
> some troubleshooting.
> > Can anyone help me find my way through? If there's documentation, I will
> gladly read it first. Up to now, I found only fuzzy things.
> > 
> > Thanks a lot!
> > Thomas
> > 
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