[Linux-cluster] gfs and fencing

[Rick Stevens]

On Wed, 2005-11-16 at 12:14 +0300, Denis Medvedev wrote:
> Lon Hohberger wrote:
> 
> >If you don't care about having to do manual intervention, you can use
> >manual fencing.  However, I *strongly* recommend against it.  IIRC,
> >there are several example configurations for different power switches in
> >the archive for this mailing list.
> >
> >  
> >
> Why not have ssh -like fencing? On a separate channel a ssh command can 
> be issued to another host to reboot or to just kill cluster processes?
> In Linux-HA stonith has a ssh feature.
> Moreover, why not have a fence_stonith which will invoke stonith as a 
> fencing agent?

You can write any fencing agent you want and, in fact, there is an ssh
fencing agent.  However, you can't absolutely rely on a misbehaving node
paying attention to ssh commands.  In fact, you can't rely on such a
node doing _anything_ you tell it to do.

You can, however, rely on an external device doing something to isolate
the node.  This could be shutting off the power to the node (via a
network-capable power distribution box) or isolating it from the network
(via a network switch) or the SAN (via the fiber switch), and that's why
these are the preferred mechanisms rather than an ssh command or
something of that ilk.

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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-         Okay, who put a "stop payment" on my reality check?        -
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