[Linux-cluster] GFS without CS?

[Steven Whitehouse]

Hi,

On Tue, 2009-09-22 at 15:28 +0200, Edgar Matzinger wrote:
> Hi Marc,
> 
> On 09/22/09 13:23:47, Marc - A. Dahlhaus wrote:
> > Hello Edgar,
> > 
> > 
> > CS is needed because it contains the service (cman) that configures
> > the
> > participation of nodes in your cluster and also enables your nodes to
> > communicate about changes they want to do an the shared filesystem.
> 
> Then GFS is not a cluster filesystem. It is just a filesystem.
> It was my perception that GFS was a stand alone application.
> Why? Because GFS supports up to 300 nodes (found in Oracle 9i RAC and
> the Red Hat Global File System). And CS "only" 32
> (http://www.redhat.com/cluster_suite/). Thinking about it: maybe
> 300 nodes mean something different. Oracle RAC does the replication
> and not GFS....
> 
I think there is some confusion here... the limit on the number of nodes
supported (currently) depends on cluster suite. Also, the number of
nodes supported is a different thing from the theoretical total number
of nodes. Larger configurations may well work, its just that we don't
regularly test such configurations.

> 
> > Also it contains the method to remove failing nodes from 
> > participating
> > in your cluster. This all is mandatory for a cluster filesystem.
> > 
> 
> No, it's mandatory for a cluster. GFS itself should embed the changes
> to files, directories, etc. in it's protocol used between the nodes.
> 
The cluster suite provides part of that protocol. It also provides
safeguards (i.e. fencing) for operations which would otherwise risk
corrupting the filesystem.

> > Please go ahead and read the available documentation if you have
> > further
> > interests in it here: http://sourceware.org/cluster
> > 
> 
> OK, will take a look, cu l8r, Edgar.

Steve.