Re: [Xen-users] Debian Etch Xen Cluster (DRBD, GNBD, OCFS2, iSCSI, Heartbeat?)

[Simon Capstick <simon@xxxxxxxxxxxxxxxx>]

Nico Kadel-Garcia wrote:
> Goswin von Brederlow wrote:
> > Dominik Klein <dk@xxxxxxxxxxxxxxxx> writes:
> >
> >  
> > > Mehdi AMINI schrieb:
> > >    
> > > > > Just remember, if something goes wrong in such a way that the 
> > > > > domain is
> > > > > active on both nodes at the same time with read/write access to the
> > > > > filesystem, you *will* *destroy* the filesystem and will need to 
> > > > > restore
> > > > > from backup. No amount of fscking will help you.
> > > > >         
> > > > This is precisely the goal of OCFS, each node can mount a block device
> > > > read/write at the same time :)
> > > >       
> > > But still, you don't want to have two servers write to the root
> > > filesystem simultaneusly, do you?
> > >     
> > 2 Things to think about:
> >
> > 1) Do what you would do without xen. Throw the power switch.
> >
> > That means you have to teach stonit or heartbeat about xen and the
> > power switch becomes "xm destroy" on the other node instead of a real
> > power switch.
> >
> > 2) Would it make sense to have a bit in the lvm headers to show that a
> > volume is active and have cluster lvm respect that bit and prevent a
> > second activation if run wihtout force?
> >
> > Maybe instead of a bit an UUID of the activator would be best. If you
> > can get a UUID that differs between the physical machines running the
> > domUs.
> >
> > MfG
> >         Goswin
> >   
> Hmm. You know, you can rename an LVM partition while Xen has it mounted. 
> This might be a useful trick to prevent another Xen guest from mounting it.
I assume you would need CLVM on the DomUs to do this, otherwise the lv 
rename would only be local to that particular Dom0.  Does someone that 
uses CLVM know whether you can do this?
Simon

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