[Linux-cluster] RE: < fecing with out any hardware? >

[Bowie Bailey]

Arnd wrote:
> Bowie Bailey wrote:
> > Pool Lee, Mr <14117614 at sun.ac.za> wrote:
> > > What about software fencing? Is it really nesasary to be hardware!
> > 
> > Your choices are limited by your configuration.  The only options
> > that can be used with any configuration are manual and power.
> 
> I was testing a few possibilities of fencing. GFS expects from the
> fencing script the status "0" to decide if it was successfull. So you
> can specify any script by your own in the cluster.conf. (Please
> correct me, if I'm wrong)
> 
> This script can be an automatic login to the failed server (ssh,
> rlogin, serial console) which can execute any remote operation (for
> example unload the module of the SAN-device) or causing an kernel
> panic (which is the fencing-method in ocfs2 ;-) ).
> 
> Your fencing-script must assure that the failed host doesn't have
> access to the filesystem anymore!

I'm not an expert on the topic.  I just use the built-in stuff.  But
my understanding is that you can write your own fence script without
too much trouble.  You just have to be careful and make sure that it
is bulletproof.

If your script relies on an ssh connection to the failed server and
the failed server is not responding to ssh, then the fencing fails and
the entire cluster must stop and wait for manual intervention.

-- 
Bowie