The cause of this outage was due to the hypervisor rebooting unexpectantly. This caused approx. 14 minutes of downtime. The montreal2000 cluster has had 100% uptime for over 1 year prior to this 14 minute outage. Sysadmins have been monitoring & are now listing the server as stable.
Issues seems to have been resolved, more details here once available.
We're currently investigating a possible network issue with the montreal2000 cluster. More details will be posted here once the data centre team investigates.