[Linux-cluster] gfs and fencing

Ryan Thomson thomsonr at ucalgary.ca
Tue Nov 15 19:51:55 UTC 2005


Hi Jeff,

I believe the theory is that if a node is down (other nodes can't
contact it) it is fenced to ensure that it is not still writing to the
volume(s) outside of the cluster environment (file locking, etc). Sure,
multiple systems can read and write the same volumes at the same time
with GFS but they do so in a co-ordinated fashion where the nodes must
communicate between themselves to make it work reliably.

Of course, I could be completely wrong.

--
Ryan

On Tue, 2005-11-15 at 07:50 -0800, Jeff Dinisco wrote:
> I'm trying to implement gfs on FC4.  I'm following the redhat docs.  I
> do not have the gui.  
> 
> I'm confused about the fencing piece.  It implies that fencing is
> required to allow a service to run on only a single node in a cluster
> which ensures data integrity.  Makes sense if your data resides on
> ext3 or an equivalent.  But it seems to defeat the purpose of GFS.  
> 
> In fact, I really only want to utilize gfs and don't want my app to be
> a service or eligible for failover.  I basically want 3 nodes to serve
> data from the same filesystem.  If an app/service/node crashes or
> fails it's fine, I'll still have 2 serving the same data via the same
> apps.  
> 
> So my questions are, how should I configure fencing?  Are there
> aspects of the cluster I should/can leave out of the mix since I
> really only want gfs functionality, not ha functionality.  Thanks
> 
> Jeff
> 
> --
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> Linux-cluster at redhat.com
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