*6.11.2 Correlated failures*

*Disasters* that affect a specific area can lead to vast service interruption, and consequently, many customers have to be recovered by CSPs. In this case, it is possible that related servers cannot handle all the customers' requests. Therefore, it can be critical to multiplex customers' data of the same area in different servers. One major challenge in this case is how to distribute customers' traffic and data between cloud servers to minimize correlated failure risks with respect to required QoS for each server and also cloud SLAs [14].
