When datacenters are pushed to their limits of operational efficiency, reducing failure rates becomes critical for maintaining high levels of healthy server operation. In this experience report, we present a dense storage case study from a large population of servers housing tens of thousands of disk drives. Previous studies have presented divergent results concerning correlation between temperature and hard disk drive failures. In our paper, we specifically establish correlation between temperatures and failures observed at different location granularities: a) inside drive locations in a server chassis, b) across server locations in a rack and c) across multiple racks in a datacenter. We also establish that temperature exhibits a stronger correlation to failures compared to the correlation of disk utilization with drive failures. Thus, we show that temperature-aware server and datacenter design plays a pivotal role in datacenter reliability. Following our case study, we present a reliability model for estimating hard disk drive failures correlated with the datacenter operating temperature. We use a physical Arrhenius model with empirically derived coefficients for our model. We show an application of the model for selecting the datacenter inlet temperature setpoint for two different server storage configurations. Finally, with the help of a datacenter cost discussion, we highlight the need to incorporate reliability-aware datacenter design for increased efficiency in large scale datacenters.