[ClusterLabs] DLM fencing

[G Spot]

Hi Ken,

Am trying to create shared storage with clvm/gfs2 and when I try to fence I
only see scsi option but my storage is conencted through FC is there any
otherways can I fence my 1G stonith device other than scsi?

On Mon, Feb 8, 2016 at 2:03 PM, Digimer <lists at alteeve.ca> wrote:

> On 08/02/16 01:56 PM, Ferenc Wágner wrote:
> > Ken Gaillot <kgaillot at redhat.com> writes:
> >
> >> On 02/07/2016 12:21 AM, G Spot wrote:
> >>
> >>> Thanks for your response, am using ocf:pacemaker:controld resource
> >>> agent and stonith-enabled=false do I need to configure stonith device
> >>> to make this work?
> >>
> >> Correct. DLM requires access to fencing.
> >
> > I've ment to explore this connection for long, but never found much
> > useful material on the subject.  How does DLM fencing fit into the
> > modern Pacemaker architecture?  Fencing is a confusing topic in itself
> > already (fence_legacy, fence_pcmk, stonith, stonithd, stonith_admin),
> > then dlm_controld can use dlm_stonith to proxy fencing requests to
> > Pacemaker, and it becomes hopeless... :)
> >
> > I'd be grateful for a pointer to a good overview document, or a quick
> > sketch if you can spare the time.  To invoke some concrete questions:
> > When does DLM fence a node?  Is it necessary only when there's no
> > resource manager running on the cluster?  Does it matter whether
> > dlm_controld is run as a standalone daemon or as a controld resource?
> > Wouldn't Pacemaker fence a failing node itself all the same?  Or is
> > dlm_stonith for the case when only the stonithd component of Pacemaker
> > is active somehow?
>
> DLM is a thing onto itself, and some tools like gfs2 and clustered-lvm
> use it to coordinate locking across the cluster. If a node drops out,
> the cluster informs dlm and it blocks until the lost node is confirmed
> fenced. Then it reaps the lost locks and recovery can begin.
>
> If fencing fails or is not configured, DLM never unblocks and anything
> using it is left hung (by design, better to hang than risk corruption).
>
> One of many reasons why fencing is critical.
>
> --
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person without
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>
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