We consider the use of non-volatile memories in the form of burst buffers for resilience in supercomputers. Their cost and limited lifetime demand effective use and appropriate provisioning. We develop an analytic model for the behavior of workloads on systems with burst buffers, and use it to explore questions of cost-effective provisioning, and missiondirected allocation of burst-buffer (SSD) lifetime.First, our results show that system efficiency can be increased by as much as 14% by considering a global perspective (workload mix, job size) for SSD lifetime allocation. Second, with size-based and system-efficiency based lifetime allocation, large jobs suffer as much as 40% job efficiency loss; job-efficiency based allocation must increase their allocations by 50% to eliminate this disparity. Finally, further results suggest that underprovisioning SSD lifetime (only 10-20% of the "optimum" as defined by per-job requirements without resource constraint) is sufficient to produce 90% system efficiency at failure rates three times that of current systems.