If Lustre is the answer, you're probably asking the wrong question. Unless that question involves short life-span, massively parallel swap-outs from one weapons simulation to another.
I write this not as storage religion (of which there's far too much), but to warn away those who haven't experienced the many kinds of data (and stomach lining) loss that come with being a Lustre admin.
Have a look at Open vStorage (http://www.openvstorage.com). Some highlights: open-source, core is battle proven for more than 7 years, performance, scales across datacenters , unlimited snapshots, ...
https://en.wikipedia.org/wiki/Clustered_file_system#Distribu...
https://en.wikipedia.org/wiki/Object_storage