Green and Low-Risk Content Placement in Optical Content Delivery Networks.

With the rapid growth of content-based network services, there is increasing interest in reducing the emissions associated with brown-energy consumption in Content Delivery Networks (CDNs). At the same time, content needs to be placed in safe Data Center (DC) locations, which are unlikely to be hit by disasters. Further risk reduction is achieved using content replication which provides inter-DC content redundancy. Unfortunately, there is contention between the objectives of brown-energy minimization and risk reduction since replicating content increases brown-energy consumption. To address these contradictory issues, we leverage the concept of content fragmentation used inside DCs and propose an inter-DC Content Fragmentation (CF) scheme which aims to achieve brown-energy saving by reducing storage overhead while maintaining low risk compared to basic replication schemes. We also propose a Green and Low-Risk Content Placement approach (GR-CP) to address the tradeoff between brown-energy consumption and disaster risk. Both CF and replication schemes are implemented in GR-CP and evaluated over a range of content popularity and redundancy levels. Our results show that CF outperforms replication scheme except when content popularity is high and the risk constraint is stringent. When popularity and risk are both low, CF can save more brown energy by using low-redundancy fragmentation techniques.