Two heads are better than one! :)

[Joseph Landman]

On Thu, 2002-10-31 at 20:56, Bob Drzyzgula wrote:

> Thus, the question becomes whether any of the various
> cluster APIs and services such as PVM, MPI, BPROC, PBS,
> etc. are dependant on the selection of a single, exclusive
> master. Clearly if multiple simultaneously operating
> masters are tolerated in the API, you can just have
> multiple head nodes which are available all the time. If
> an API requires a single master, one might have to effect
> some sort of manual switch-over in the event of a head
> node failure; this would then raise the question of the
> complexity of such a switch-over, e.g. would compute node
> reconfiguration be required or would it simply be a matter
> of starting up the controller service on a new system.

Hi Bob:

  It is more complex than that, in that you would need to preserve state
changes over the length of the program, and PVM/MPI/et al do not
preserve this state information.  The folks at LANL had a fault tolerant
MPI at one point, but I haven't heard much of it recently.

Joe

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Joseph Landman, Ph.D
Scalable Informatics LLC
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