GFS2 storage unavailable to both cluster nodes

Issue

We had an instance whereby GFS2 storage was unavailable to both nodes in a cluster environment. All read/write operations to the SAN timed out during this time. Restarting node 2 brought normal operation back to node 1 & 2.
How can I ensure this doesn't happen in future?

Red Hat Enterprise Linux Server 5 (with the High Availability or Resilient Storage Add Ons)

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