Clustering Goals
================
$Id: goals.txt,v 1.4 1999/12/17 14:52:15 sct Exp $

The primary goals of the cluster infrastructure project are to:

* Provide hooks which allow cluster-wide coordination between
  arbitrary services.  Implementing those services is a separate
  problem.

* Provide a strong concept of cluster membership, with synchronised,
  transactional transitions between cluster states when a new node joins
  the cluster or an existing node dies.


The long term "vision" includes much which is not anticipated in the
initial implementation.  Some of this will be scheduled for future
implementation.  We also want the clustering services to accommodate
third-party services which may never be part of this cluster core
itself, but which will place certain requirements on the clustering
which we have to take into account here.  We are particularly concerned
with:

* Scalability, both up and down.  We want to be able to cluster a pair
  of 486es to provide highly available departmental web services out of
  the Linux cupboard that a sysadmin installed once.  We want to be able
  to cluster massive numbers (tens or hundreds of thousands) of nodes
  for Massively Parallel Processing (note that we only want to deal with
  the admin/HA aspects of this --- the MPP interconnect is somebody
  else's problem --- but this still implies a need for hierarchical
  clusters).

* Scalable cluster filesystem support.  Within one cluster segment,
  GFS is the sort of implementation we want to grow a cluster FS out
  of, with shared disk access on top of cluster-wide shared block
  devices and shared software raid.

  On top of that, a mechanism such as AFS or CODA for migrating files
  between cluster segments will be necessary: the shared disk model
  does not scale well once distant nodes become involved.

* Provide a set of sufficiently simple APIs, without actually enforcing
  the way they are used, that nobody in their right mind will consider
  using any other basic cluster infrastructure to base their HA
  solutions on.  (Well, it can't hurt to dream, can it?)