MPI-over-Grid

Talk given at 9th AstroGrid-D Meeting
in Potsdam, 25th February 2008

Overview

MPI Message Passing Interface

• focus is on parallel communications.
• machines must at least be running at the same time.
• many applications require synchronized communication, this means machines have to run at about the same speed.
• but there are many applications that don't require such synchronization.

Grid technology

• primary advantage: authentication via trust mechanism
• some nice tools: job submission, fast file transfer

How can they go together

• MPI-Over-Grid
• submitting MPI jobs to cluster using grid technology

Requirements

• each node must be a Grid resource
• requires knowledge of architecture and Globus flavor on nodes ports for Globus 2 gateway

Job submission over grid

• big advantage: abstracts away the cluster resource manager.
• important for those who run jobs on many different clusters.

Issues

• synchronization (application dependent)
• if nodes are remote, bandwidth lower than on cluster
• communications overhead on fast cluster interconnect
• job management
• administration, installation of Globus

Topologies

heterogeneous nodes

• synchronization issues
• job/utilization permission issues

tightly communicating clusters

• Synchronization issues
• Not clear where grid comes in here... could communicate without grid authentication
• Some communications overhead.

MPI-over-grid on remote clusters

• each node must be a grid resource, but current installation of Globus makes this difficult.

hierarchical

• Compute nodes not grid resources. only head nodes are.
• MPI jobs run on clusters, each cluster with controlling process on head node communicates intermediate results among clusters

Problems