On Wednesday 15th March between 10am and 4pm, we will be upgrading the "nova" services in QRIScloud as part of the NeCTAR mandated OpenStack Mitaka upgrade sequence.
We expect there will be no detectable service interruptions. (The QRIScloud "nova" services are triply redundant and will be upgraded one at a time, with the option of rollback in the event of problems.) In the unlikely event of a "nova" service interruption, this should only affect server management actions; e.g. launching new instances, taking snapshots and so on. Existing running instances should be unaffected.
UPDATE - 2016-03-20 - The upgrades were performed without any issues.